Some X Window Icons don't work

[tenfourty]

Running on Fedora 33 (and 34 beta) the recent window widget is not able to detect the icon of the window which means some recent windows aren't shown.

You can reproduce this with the Spotify app by switching to it and then away.

There is an error message on the console:
Could not find icon for window 113246215.

From a quick look at the code it seems that if there is an error getting the icon you ignore the window, but perhaps you could try to get the window title and insert some text instead?