In the commit d678ba1103 we added
gif parsing support on paste, but we also slightly changed the
isComposer check there, along with a change in chat this caused
isComposer to be true (which is correct), however the event we fire
is composer:insert-text which the chat composer does not pick up.
Instead, we should use composerEventPrefix if it is present to
fire the insert-text event, and if it is not present (e.g. for
some custom composer that someone has implemented) fall back to
the default. There is a companion commit for chat to handle this
change there.