Chatty 0.7.0 crashes on Librem5 when typing ':)' in a matrix room

purism@pureos:~$ dpkg-query -W chatty
chatty	0.7.0-1pureos1

On Librem5 running PureOS Byzantium.

When typing (external keyboard via usb and squeekboard tested) a colon followed by a closing round bracket (classical ascii smiley ':)') chatty crashes.

When called from the terminal using chatty -d I get the following message when the error occurs:

Gtk[23181]: WARNING: Invalid text buffer iterator: either the iterator is uninitialized, or the characters/pixbufs/widgets in the buffer have been modified since the iterator was created.
You must use marks, character numbers, or line numbers to preserve a position across buffer modifications.
You can apply tags and insert marks without invalidating your iterators,
but any mutation that affects 'indexable' buffer contents (contents that can be referred to by character offset)
will invalidate all outstanding iterators
signum 11: Segmentation fault

Update:

• Graphical Emoticons needs to be turned on to reproduce this
• if Graphical Emoticons is activated chatty crashes with the same error in PureOS Byzantium on a Librem14 as well