Emoji window mouse pointer bug
v1.0.9/gajim-default-nightly, 20180827-1 Debian GNU/Linux 9.5 (Stretch)
When you are using the single-window layout, open the emoji panel, and try to insert certain emojis by clicking (specifically those which appear over the separating/resizing line between the contacts list and the messages area), the emojis aren't inserted, because the cursor turns into a resizing pointer.
This bug occurred with both the old emoji window and the new one.
I was informed that this is a GTK bug. To report it to GTK, a minimal reproducible example will have to be created. If anyone can do that, this crease can be ironed out of Gajim.