If CheckWindowOptionalNeed is called consecutively (and the first removes optional), then
we will SEGFAULT. This can happen in XQuartz because ReparentWindow will call
pScreen->ReparentWindow which can DeleteProperty which will CheckWindowOptionalNeed... then
ReparentWindow will call it again later indiscriminantly.
(cherry picked from commit b608c864ccc59628bd33c033393121b61580460e)