Fix missing notifier when inserting keyframe

Reported by Sebastian Koenig in IRC
Fix Bevel multisegment profile bugs T39184, T37502 and last part of T40365.

When doing a 'weld' type join where there are two non-beveled edges
in the same plane one beveled one but not the other, then there
should be a curved profile; bug was creating a straight one.
Fix a warning in carve by initializing var
Bake-API: removal of unecessary UV tests, as suggested by Campbell Barton