Matrix -> Discord images get dropped if they don't have a caption

[SwirlyStone5877]

Describe the bug
Images sent on Matrix without a caption/description don't get sent to Discord.

To Reproduce
Steps to reproduce the behavior:

1. send an image with no caption on matrix
2. watch it fail to send on discord

Expected behavior
It should send to Discord as usual.

Screenshots/debug logs

[0030] DEBUG matrix:       [handleMessageEvent:bridge/matrix/matrix.go:631] == Receiving message event: &event.Event{StateKey:(*string)(nil), Sender:"@swirly:architectenterprises.net", Type:event.Type{Type:"m.room.message", Class:1}, Timestamp:1774707162044, ID:"$ZU02SSk9NWUyKWCDyE50mA60oPWNUBIzcYbLVTdiprI", RoomID:"!rKOmKoXWrMjQVRvdrz:architectenterprises.net", Content:event.Content{VeryRaw:json.RawMessage{0x7b, 0x22, 0x6d, 0x73, 0x67, 0x74, 0x79, 0x70, 0x65, 0x22, 0x3a, 0x22, 0x6d, 0x2e, 0x69, 0x6d, 0x61, 0x67, 0x65, 0x22, 0x2c, 0x22, 0x66, 0x69, 0x6c, 0x65, 0x6e, 0x61, 0x6d, 0x65, 0x22, 0x3a, 0x22, 0x49, 0x4d, 0x47, 0x5f, 0x45, 0x30, 0x36, 0x34, 0x38, 0x2e, 0x4a, 0x50, 0x47, 0x22, 0x2c, 0x22, 0x62, 0x6f, 0x64, 0x79, 0x22, 0x3a, 0x22, 0x49, 0x4d, 0x47, 0x5f, 0x45, 0x30, 0x36, 0x34, 0x38, 0x2e, 0x4a, 0x50, 0x47, 0x22, 0x2c, 0x22, 0x70, 0x61, 0x67, 0x65, 0x2e, 0x63, 0x6f, 0x64, 0x65, 0x62, 0x65, 0x72, 0x67, 0x2e, 0x65, 0x76, 0x65, 0x72, 0x79, 0x70, 0x69, 0x7a, 0x7a, 0x61, 0x2e, 0x6d, 0x73, 0x63, 0x34, 0x31, 0x39, 0x33, 0x2e, 0x73, 0x70, 0x6f, 0x69, 0x6c, 0x65, 0x72, 0x22, 0x3a, 0x66, 0x61, 0x6c, 0x73, 0x65, 0x2c, 0x22, 0x69, 0x6e, 0x66, 0x6f, 0x22, 0x3a, 0x7b, 0x22, 0x77, 0x22, 0x3a, 0x37, 0x32, 0x33, 0x2c, 0x22, 0x68, 0x22, 0x3a, 0x37, 0x31, 0x31, 0x2c, 0x22, 0x6d, 0x69, 0x6d, 0x65, 0x74, 0x79, 0x70, 0x65, 0x22, 0x3a, 0x22, 0x69, 0x6d, 0x61, 0x67, 0x65, 0x2f, 0x6a, 0x70, 0x65, 0x67, 0x22, 0x2c, 0x22, 0x73, 0x69, 0x7a, 0x65, 0x22, 0x3a, 0x32, 0x31, 0x38, 0x30, 0x39, 0x38, 0x2c, 0x22, 0x78, 0x79, 0x7a, 0x2e, 0x61, 0x6d, 0x6f, 0x72, 0x67, 0x61, 0x6e, 0x2e, 0x62, 0x6c, 0x75, 0x72, 0x68, 0x61, 0x73, 0x68, 0x22, 0x3a, 0x22, 0x55, 0x58, 0x4f, 0x67, 0x34, 0x24, 0x2d, 0x55, 0x2d, 0x70, 0x52, 0x6a, 0x54, 0x30, 0x5f, 0x4e, 0x74, 0x52, 0x49, 0x55, 0x2d, 0x70, 0x4d, 0x7b, 0x4d, 0x7b, 0x52, 0x6a, 0x3f, 0x48, 0x4d, 0x78, 0x52, 0x6a, 0x25, 0x4d, 0x22, 0x7d, 0x2c, 0x22, 0x75, 0x72, 0x6c, 0x22, 0x3a, 0x22, 0x6d, 0x78, 0x63, 0x3a, 0x2f, 0x2f, 0x61, 0x72, 0x63, 0x68, 0x69, 0x74, 0x65, 0x63, 0x74, 0x65, 0x6e, 0x74, 0x65, 0x72, 0x70, 0x72, 0x69, 0x73, 0x65, 0x73, 0x2e, 0x6e, 0x65, 0x74, 0x2f, 0x41, 0x62, 0x57, 0x75, 0x71, 0x75, 0x7a, 0x53, 0x73, 0x45, 0x52, 0x56, 0x7a, 0x4e, 0x4e, 0x70, 0x75, 0x4f, 0x52, 0x53, 0x46, 0x72, 0x41, 0x47, 0x22, 0x2c, 0x22, 0x6d, 0x2e, 0x72, 0x65, 0x6c, 0x61, 0x74, 0x65, 0x73, 0x5f, 0x74, 0x6f, 0x22, 0x3a, 0x7b, 0x7d, 0x7d}, Raw:map[string]interface {}{"body":"IMG_E0648.JPG", "filename":"IMG_E0648.JPG", "info":map[string]interface {}{"h":711, "mimetype":"image/jpeg", "size":218098, "w":723, "xyz.amorgan.blurhash":"UXOg4$-U-pRjT0_NtRIU-pM{M{Rj?HMxRj%M"}, "m.relates_to":map[string]interface {}{}, "msgtype":"m.image", "page.codeberg.everypizza.msc4193.spoiler":false, "url":"mxc://architectenterprises.net/AbWuquzSsERVzNNpuORSFrAG"}, Parsed:(*event.MessageEventContent)(0x110d5b5da840)}, Redacts:"", Unsigned:event.Unsigned{PrevContent:(*event.Content)(nil), PrevSender:"", Membership:"join", ReplacesState:"", Age:28, TransactionID:"", Relations:(*event.Relations)(nil), RedactedBecause:(*event.Event)(nil), InviteRoomState:[]*event.Event(nil), BeeperHSOrder:0, BeeperHSSuborder:0, BeeperHSOrderString:(*event.BeeperEncodedOrder)(nil), BeeperFromBackup:false, ElementSoftFailed:false, ElementPolicyServerSpammy:false}, Mautrix:event.MautrixInfo{EventSource:34, TrustState:0, ForwardedKeys:false, WasEncrypted:false, TrustSource:(*id.Device)(nil), ReceivedAt:time.Date(1, time.January, 1, 0, 0, 0, 0, time.UTC), EditedAt:time.Date(1, time.January, 1, 0, 0, 0, 0, time.UTC), LastEditID:"", DecryptionDuration:0, CheckpointSent:false, IgnoreState:false}, ToUserID:"", ToDeviceID:""}
[0030] DEBUG matrix:       [func2:bridge/matrix/matrix.go:454] Sync() returned ProcessResponse panicked! since=s114682_1884413_2743_223770_34798_291_5412_109774_0_114_1_1 panic=runtime error: invalid memory address or nil pointer dereference
goroutine 57 [running]:
runtime/debug.Stack()
        /usr/lib/go/src/runtime/debug/stack.go:26 +0x5e
maunium.net/go/mautrix.(*DefaultSyncer).ProcessResponse.func1()
        /home/server/go/pkg/mod/maunium.net/go/mautrix@v0.26.1/sync.go:90 +0x58
panic({0x235a6c0?, 0x4308a60?})
        /usr/lib/go/src/runtime/panic.go:860 +0x13a
github.com/matterbridge-org/matterbridge/bridge/matrix.(*Bmatrix).handleReply(0x110d5a642c00, 0x110d5a45b830?, {{0x110d5aa9d0f0, 0xd}, {0x110d5a3536b0, 0x2c}, {0x110d5ad85c00, 0x6}, {0x110d5a4242c0, 0x20}, ...})
        /home/server/matterbridge/bridge/matrix/matrix.go:520 +0xf4
github.com/matterbridge-org/matterbridge/bridge/matrix.(*Bmatrix).handleMessageEvent(0x110d5a642c00, {0x2a1d860, 0x110d5a696390}, 0x110d5aa62000)
        /home/server/matterbridge/bridge/matrix/matrix.go:699 +0x54e
maunium.net/go/mautrix.(*DefaultSyncer).Dispatch(0x110d5a8d2050, {0x2a1d860, 0x110d5a696390}, 0x110d5aa62000)
        /home/server/go/pkg/mod/maunium.net/go/mautrix@v0.26.1/sync.go:169 +0xd0
maunium.net/go/mautrix.(*DefaultSyncer).processSyncEvent(0x110d5a8d2050?, {0x2a1d860?, 0x110d5a696390?}, {0x110d5b5e17d0?, 0x217e000?}, 0x110d5aa62000?, 0x22?, 0x0?)
        /home/server/go/pkg/mod/maunium.net/go/mautrix@v0.26.1/sync.go:159 +0x12c
maunium.net/go/mautrix.(*DefaultSyncer).processSyncEvents(...)
        /home/server/go/pkg/mod/maunium.net/go/mautrix@v0.26.1/sync.go:128
maunium.net/go/mautrix.(*DefaultSyncer).ProcessResponse(0x110d5a8d2050, {0x2a1d828, 0x4506a80}, 0x110d5a351b30, {0x110d5ab98080, 0x3b})
        /home/server/go/pkg/mod/maunium.net/go/mautrix@v0.26.1/sync.go:108 +0x4c8
maunium.net/go/mautrix.(*Client).SyncWithContext(0x110d5a72d6c0, {0x2a1d828, 0x4506a80})
        /home/server/go/pkg/mod/maunium.net/go/mautrix@v0.26.1/client.go:306 +0x61d
maunium.net/go/mautrix.(*Client).Sync(...)
        /home/server/go/pkg/mod/maunium.net/go/mautrix@v0.26.1/client.go:221
github.com/matterbridge-org/matterbridge/bridge/matrix.(*Bmatrix).handlematrix.func2()
        /home/server/matterbridge/bridge/matrix/matrix.go:452 +0x45
created by github.com/matterbridge-org/matterbridge/bridge/matrix.(*Bmatrix).handlematrix in goroutine 33
        /home/server/matterbridge/bridge/matrix/matrix.go:446 +0xa45
, retrying in 5 seconds...

Environment (please complete the following information):

• OS: Arch Linux
• Matterbridge version: add correct audio handling for matrix #195

Additional context
Relevant portions of config:

#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#~         __  ______ ___________________  ___  ___  _______  _________        ~
#~        /  |/  / _ /_  __/_  __/ __/ _ \/ _ )/ _ \/  _/ _ \/ ___/ __/        ~
#~       / /|_/ / __ |/ /   / / / _// , _/ _  / , _// // // / (_ / _/          ~
#~      /_/  /_/_/ |_/_/   /_/ /___/_/|_/____/_/|_/___/____/\___/___/          ~
#~                                                                             ~
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[general]
RemoteNickFormat="{TENGO}"
MediaDownloadPath="/home/server/fs/files/matterbridge"
MediaDownloadSize=4294967296 #4gb
MediaServerDownload="https://fs.swirly.architectenterprises.net/matterbridge"
MediaDownloadBlacklist=[]

[tengo]
RemoteNickFormat="/home/server/matterbridge/remotenickformat.tengo"

[matrix.fc]
Server="https://architectenterprises.net"
MxID="@swirly-mattermost:architectenterprises.net"
Token="sthsrtdhsrthh"
DeviceID="AMNNVPMVKJ"
HTMLDisable=false
NoHomeServerSuffix=true
EditSuffix=" (edited)"
#...
[discord.yumetaro]
Token="dwuihfiewgufk"
Server="989923775715885127"
AutoWebhooks=false
PreserveThreading=true
ShowEmbeds=true
UseLocalAvatar=["discord", "matrix"]
QuoteFormat="↳\\[Replying to <strong>{QUOTENICK}</strong>\\] <br> <details><summary>Quoted content</summary>{QUOTEMESSAGE}</details> <br> {MESSAGE}"
#...
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#~                        Yumetaro's Internet Land                             ~
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[[gateway]]
name="yumetaro-announcements"
enable=true

[[gateway.in]]
account="discord.yumetaro"
channel="announcements-news"

[[gateway.in]]
account="discord.yumetaro"
channel="small-news"

[[gateway.out]]
account="matrix.fc"
channel="!GZpjBKigImLXtXqaPw:architectenterprises.net"

#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[[gateway]]
name="yumetaro-texttypevote"
enable=true

[[gateway.inout]]
account="discord.yumetaro"
channel="text-type-vote"

[[gateway.inout]]
account="matrix.fc"
channel="!sJGInDNXMYXvnFyRPX:architectenterprises.net"

#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[[gateway]]
name="yumetaro-yourwips"
enable=true

[[gateway.inout]]
account="discord.yumetaro"
channel="your-wips"

[[gateway.inout]]
account="matrix.fc"
channel="!ALJsRnOPcCrDxFDYgc:architectenterprises.net"

#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[[gateway]]
name="yumetaro-otherpeoplesworks"
enable=true

[[gateway.inout]]
account="discord.yumetaro"
channel="other-peoples-works"

[[gateway.inout]]
account="matrix.fc"
channel="!GdlEHUTcHTfkkhXMtk:architectenterprises.net"

#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[[gateway]]
name="yumetaro-yourworks"
enable=true

[[gateway.inout]]
account="discord.yumetaro"
channel="your-works"

[[gateway.inout]]
account="matrix.fc"
channel="!SINIzSVkfJirFiMMya:architectenterprises.net"

#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[[gateway]]
name="yumetaro-hobbyworks"
enable=true

[[gateway.inout]]
account="discord.yumetaro"
channel="hobby-works"

[[gateway.inout]]
account="matrix.fc"
channel="!VCwDEuRPSwvVKgLMSk:architectenterprises.net"

#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[[gateway]]
name="yumetaro-thecentral1"
enable=true

[[gateway.inout]]
account="discord.yumetaro"
channel="the-central-1"

[[gateway.inout]]
account="matrix.fc"
channel="!rKOmKoXWrMjQVRvdrz:architectenterprises.net"

#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[[gateway]]
name="yumetaro-thecentral2"
enable=true

[[gateway.inout]]
account="discord.yumetaro"
channel="the-central-2"

[[gateway.inout]]
account="matrix.fc"
channel="!UDFbiWyTaEPpVfqkjE:architectenterprises.net"

#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[[gateway]]
name="yumetaro-offtopic"
enable=true

[[gateway.inout]]
account="discord.yumetaro"
channel="off-topic"

[[gateway.inout]]
account="matrix.fc"
channel="!zHaijAafXmDrleFKnG:architectenterprises.net"

#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[[gateway]]
name="yumetaro-shitposting"
enable=true

[[gateway.inout]]
account="discord.yumetaro"
channel="shitposting"

[[gateway.inout]]
account="matrix.fc"
channel="!XqkhCdiSrFrlHZmesc:architectenterprises.net"

[poVoq]

Does this also happen with the current main branch?

[SwirlyStone5877]

That PR shouldn't affect anything image-related but will test anyway.

[SwirlyStone5877]

Images still aren't sent on master.

[poVoq]

Were you able to identify a possible cause of this?

[SwirlyStone5877]

No, and as of now I can't test further.