Unnecessary time signatures not removed after Undo
1. Create an empty 4/4 score with more that one measure
2. Change time signature of one measure other than first to 3/4
3. Change first time sig to 3/4
4. The second 3/4 time sig is removed as it should.
5. Undo last operation
6. Change first time sig again to 3/4
Now the second 3/4 time sig is not removed (as it should be).