Representative sequence based editing breaks if represented sequences partially revealed

Noticed when exploring JAL-2134:
1. import feredoxin alignment, select 5 sequences and pick the middle one as representative.
2. right click on the blue triangle *below* the representative sequence and select 'reveal sequences'
--> the represented sequence group is now partially revealed.
3. Press escape to clear the current selection
4. Use shift-click-drag to insert gaps in the reference sequence
--> note that for every gap inserted in reference, two gaps are inserted in the visible representees.