Spanners not properly deleted when corresponding anchoring notes are deleted

Steps:
1- Open attached file;
2- Select the first measure (the whole measure, not individual single notes);
3- Delete (canc or Ctrl+X)
4- Select first measure and enter note input mode (press N);
5- Select 1/4 note duration (press 5) and enter four 1/4 notes;
6- The slur which was deleted in step -3- magically reappears.

Or, analogously:
1- Open attached file;
2- Select the two slurred notes (select the first and shift-select the second);
3- Delete (canc or Ctrl+X)
4- Select the (new) 2/4 pause of measure 1 and change duration to 1/4+1/4 (by pressing 5);
5- The slur which was deleted in step -3- magically reappears.

In the debugger, the slur is still present, but it loses the start- and end-elements.
If a hairpin is used instead of a slur, the hairpin is not deleted as well and it is still visible. It loses start- and end-elements as well when these are deleted.

MuseScore Nightly build de46b205d8, Windows 8.