Hi Drew, from my naive perspective (I have no ideas about the internals - just received a bunch of "removal from testing" messages) your suggestion to turn an error about "invalid window" into a warning seems to be an apropriate action in this case.
May be the bug could be reopened later with lower severity to make sure the issue is not totally lost for the future. Just my 2 Euro cents Andreas. -- http://fam-tille.de