Prevent crash-inducing recursion of detach due to blur events
happening when widgets with focus get destroyed, by quietly shifting
the focus to the view...(#135384, probably #124342 --- best I can tell given
imperfect information); also affects some bugs which I separately closed as
non-reproducible, but which involved such a sequence

Also fixes freezing in #92497, as we no longer try to find something
to focus when nothing is focusable..