A context area/region override would be left cleared when the context
manager exited - if the overriding value matched the current value.
- `self->ctx_init.*_is_set` members would be set even if the those
arguments weren't passed in, because the values would compare
as different to NULL (unset).
- When restoring the context, setting a window clears the area & region,
setting the area clears the region.
This wasn't taken into account - only the members that were
overridden were restored.
In the case of #110632, the window & region were detected as changed,
even though neither were overridden.
So the window & region were restored. The area however was set to it's
self and not marked as changed, so the area was left cleared from the
call that restored the window.
Resolve by fixing the check for overridden members & restoring
context members that will have been cleared indirectly.
0df7d100a3