I just tried adding an emoji to one of my pot titles and it didn’t crash. I didn’t have an emoji in there originally (before the layout update), so perhaps that’s where the issue lies?
I can create a pot with an emoji, edit that pot and delete it with no app crashes.
It seems to be isolated to pots I already have created.
Edit: I also tried deleting all emoji from an existing pot and saved it, this caused a crash. Opening the app and editing the (now emoji-less pot) and saving it still caused a crash.
A complete guess, but I think Monzo are possibly truncating the pot name in a ham-fisted way - and as emoji are technically multiple characters, they are breaking the display of an emoji that is at the truncation point. The codepoint for your light bulb emoji is U+1F4A1, and monzo might be truncating it to U+1F… for example.