Comment 7 for bug 1805361

Here is a stacktrace of hitting it on GTK+ (3). I haven't got time right now to debug it, but in case it's useful on its own, here it is!

This is in the text tool, with width set to 0mm.

Also, this behaviour is particularly unfriendly when you have focus-follow-mouse enabled, as if you have 0 in a text box, if you move the mouse out of the dialog, it loses focus and throws the alert box. If you now mouse out and then click on the dialog again, the alert is pushed behind the dialog, and you can't do anything until you move the dialog out of the way, dismiss the alert and correct the field. Any stray out of the dialog in the meantime throws the dialog again.