Usual issue of modifying the data hierarchy while iterating on it in its
outliner representation. And usual fix for this problem (only store data
to be processed during the iteration over Outliner data, and perform the
actual operation in a single call afterwards).
This commit also tries to improve a bit the 'Clear' process when applied
to a bunch of IDs, by iterating several times over the list of IDs to
clear, and only processing 'liboverrides leaves' first. That way, if
clearing a liboverride leaves turn other liboverrides into leaves, then
can also be processed that way, instead of just being reset.
Note that this is a naive and quite imperfect solution though
(dependency islands cannot be handled that way e.g.), this feature needs
a complete re-write at some point to be more complete and consistent.
Don't think this is high priority though, as it is not really that
useful in practice afaik.
Note: This should be backported to 3.6 LTS (and maybe 3.3 LTS if
applicable).
a60c1e5bb8