UGENE crashes on the msa aligning which was once failed to align

Scenario to reproduce:

1. Open "data/samples/CLUSTALW/ty3.aln.gz".
2. Start an align task with any tool, e.g. use KAlign.
3. While the aligning is performed, lock the document for editing.
4. Wait for the aligning end.
   Expected state: the aligning failed, because there is no way to apply changes for the locked document.
5. Unlock the document.
6. Start the aligning again.
   Expected state: the MSA is successfully aligned.
   Current state: a SAFE_POINT triggers, then UGENE crashes.