Anyone have similar issues?
It happened once for me with Thunar but I couldn't reproduce it. The
window in question was a progress dialog for a file copy over MTP, and
when I tried to xkill it and saw nothing happened I ran `xprop | grep PID`
to find it belonged to no process.
If you can reproduce this bug with Evolution, you should file a new bug
on rhbz.
Dridi