boxlayout: Do not infloop

boxlayout: Do not infloop

if the loop for determining max width grows too big, print an error and
abort assuming that a satisfactory value was reached.

This will cause wrong layout and might cause widgets to overlap, but it
will not infloop.

It actually works around and doesn't really fix the primary cause of the
following bugs, but good enough to close them:

Fixes: #4252
Fixes: #4517