community/wlroots: fix crash when unplugging output
If an output was unplugged of which the image was captured (e.g. with wl-mirror), an assertion blew up due to unclean handling of that event. This backports an upstream commit to fix the issue.
If an output was unplugged of which the image was captured (e.g. with wl-mirror), an assertion blew up due to unclean handling of that event. This backports an upstream commit to fix the issue.