Protobuf encoding TypeError map :<field>

[femuitar]

Tested with

• logstash-7.9.3
• logstash-codec-protobuf-1.2.2

_pb.rb
`
require 'google/protobuf'

Google::Protobuf::DescriptorPool.generated_pool.build do
add_message "XX" do
optional :timestamp, :int64, 1
map :map_string, :string, :string, 2
end
end
..........
`

will get the following error
Protobuf encoding error 2.2: Type error (#<TypeError: Invalid argument for string field.>). Will try to convert the data types. Original data: ......