When all vertex groups are *unlocked* and the Normalize All operator is
run with "Lock Active" disabled, the operator would fail with the
patently false error message "All groups are locked".
The cause was that:
1. When all vertex groups are unlocked, the lock flags array used
internally would be left empty, with the idea that a non-existent
flag indicates "unlocked".
2. The code that determined if all groups were locked was checking
if any of those flags were "unlocked".
3. In an empty array, of course no items are "unlocked", and thus
it would think all items are locked.
The fix in this PR is to also check if the flag array is empty when
determining if all groups are locked.
Pull Request: https://projects.blender.org/blender/blender/pulls/147272
af63d06739