WM_CLASS is set after the window leaves the withdrawn state

[stevendlander]

When referencing the WM_CLASS variable in xprop, it seems that evilvte has "" as the value of WM_CLASS initially, and only after the window leaves the withdrawn state does it get set correctly to Evilvte. See the following related discussion where the same thing is happening to the Spotify application on launch:

https://bbs.archlinux.org/viewtopic.php?pid=1581353#p1581353