UniqueIDUtils: Do not wrap model modification in fixMissingIDs() into a command
Creation of the command should be performed in the calling scope (and in
many cases it already is).
However, usage of commands is not supported when using the method from a
test case.
After implementing this change, Commit r23375 "moved fixMissingIDs from transfrom() can and should be reverted.
(from redmine: issue id 3369, created on 2018-04-06, closed on 2018-05-22)