When several chat boxes are open, selected emoji is inserted into all of them.

To Reproduce

1. Open several chat boxes
2. Select an emoji from one of them
3. Selected emoji is inserted into each of all open ones

Expected behavior
Selected emoji should have been inserted only into the chat box from which it has been selected.

Environment:

• Desktop
• Browser: all
• Converse.js version 9.1.0

Additional context
I think there is a link with closed PR #2841.
I did surely not check this super basic use case when @jcbrand asked me to verify the emoji feature behavior after some refactoring.
I found locally a way to fix the issue, but according the minding behind the last emoji refactoring, I'm not sure that is a good one (SilverYoCha#2)