Cross-staff slur is copied even when end anchor is not copied

Also see #83606: Copying passage with cross-staff slur causes a crash

Linux, nightly d349682
1. Open attached score.
2. Copy first measure in bass part.
3. Paste in second measure in bass part.

Expected: No copied slur, since the end anchor is not copied.
Actual: Slur is copied and is anchored to the measure rest in the first staff.

Compare to what happens when the entire first measure is copied and pasted to the second measure.

Workaround: Delete offending slurs.

Discussion:
Issue happens for cross-staff slurs.
Seems this doesn't happen for cross-voice slurs.