Assert in case of editing of a reference in the Assembly Browser

Scenario:

1. Open "Assembly/chrM.sorted.bam" in the Assembly Browser.
2. Add "Assembly/chrM.fa" as a reference.
3. Open "Assembly/chrM.fa" as in the SV
4. Delete a part of the sequence.
5. Open the AB and scroll right to the end.
   Current result: the AB didn't update the reference, so it catches an assert.
   Expected result: the AB updated the reference.

Make sure as well that everything's OK in case of the alphabet changing during the editing.