Remove some nested `if` statements to improve readablilty. My main
intention has been to improve readability and therefore making it easier
to implement changes in the future.
Seperating the symmetrize operator selection logic from the temp pointer
logic may reduces performance but it seems acceptable in this case. The
change allows focussing on the selection logic without taking care of
the temp pointers at the same time.
No functional changes.
Pull Request: https://projects.blender.org/blender/blender/pulls/106487
aaf56d7aa5