See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1030909

GTK 'ignores' errors by recording the next request number, setting the error
handler, doing the request for which error is to be ignored, recording the next
request number to determine the interval to be ignored, unsetting the error
handler, and crashing when the asynchronous error arrives.

It uses this 'ignore' facility liberally in the GTK code so synchronizing with
the X server every time an error is to be ignored would probably decrease
performance of some applications.

Setting the 'ignore' error handler once when opening the display would likely
work and potentially conflict with other applications trying to use custom
error handling.