Crash when applying change to resource

[SoMuchForSubtlety]

Issue description

The program panics when clicking "Apply" after editing a resource

panic: interface conversion: gtk.Widgetter is *gtk.Widget, not *gtk.Label [recovered]
	panic: closure error: unexpected panic caught: interface conversion: gtk.Widgetter is *gtk.Widget, not *gtk.Label

Closure added at:
	github.com/diamondburned/gotk4/pkg/gtk/v4.(*Button).ConnectClicked at github.com/diamondburned/gotk4/pkg@v0.3.0/gtk/v4/gtk.go:30781
	github.com/getseabird/seabird/internal/ui/editor.NewEditorWindow at github.com/getseabird/seabird/internal/ui/editor/window.go:68
	github.com/getseabird/seabird/internal/ui.NewClusterWindow at github.com/getseabird/seabird/internal/ui/cluster_window.go:66

goroutine 1 [running, locked to thread]:
github.com/diamondburned/gotk4/pkg/core/closure.(*FuncStack).Panicf(0xc002cba1b0, {0x3092e35, 0x1b}, {0xc00673d878, 0x1, 0x1})
	github.com/diamondburned/gotk4/pkg@v0.3.0/core/closure/funcstack.go:104 +0x908
github.com/diamondburned/gotk4/pkg/core/closure.(*FuncStack).TryRepanic(0xc002cba1b0)
	github.com/diamondburned/gotk4/pkg@v0.3.0/core/closure/funcstack.go:122 +0xc5
panic({0x2bbb920?, 0xc0071fb050?})
	runtime/panic.go:770 +0x132
github.com/getseabird/seabird/internal/ui/editor.(*EditorWindow).saveClicked(0xc002c6e700)
	github.com/getseabird/seabird/internal/ui/editor/window.go:168 +0xb0b
github.com/diamondburned/gotk4/pkg/gtk/v4._gotk4_gtk4_Button_ConnectClicked(0x50e3e5?, 0x305?)
	github.com/diamondburned/gotk4/pkg@v0.3.0/gtk/v4/gtk_export.go:2155 +0x6e
github.com/diamondburned/gotk4/pkg/gio/v2._Cfunc_g_application_run(0xbf942b0, 0x1, 0xbfcfe90)
	_cgo_gotypes.go:12555 +0x4b
github.com/diamondburned/gotk4/pkg/gio/v2.(*Application).Run.func3(0xbf942b0, 0x1, 0xbfcfe90)
	github.com/diamondburned/gotk4/pkg@v0.3.0/gio/v2/gio.go:36988 +0x67
github.com/diamondburned/gotk4/pkg/gio/v2.(*Application).Run(0xc000460018, {0xc000052090, 0x1, 0x1})
	github.com/diamondburned/gotk4/pkg@v0.3.0/gio/v2/gio.go:36988 +0x1f1
github.com/getseabird/seabird/internal/ui.(*Application).Run(0x3452a30?)
	github.com/getseabird/seabird/internal/ui/application.go:70 +0x2d
main.main()
	github.com/getseabird/seabird/main.go:31 +0xc5

Steps to reproduce

1. edit a resource (no need to change anything, just open the edit dialog)
2. click apply

System information

Seabird 0.5.1, Linux, amd64