UGENE behavior on deleting object and document

Scenario 1:

1. Open "data/samples/CLUSTALW/COI.aln".
2. Use context menu {Add->Sequence from file...}

   .
   Expected: "Open file with sequences" dialog appeared.

3. Select file "_common_data\fasta\PF07724_full_family.fa".
4. Press "Open".
5. Delete the alignment object
   Current state: an add task is canceled, the object is deleted.

Scenario 2:
The same, but delete the document instead of the object.
Current state: a message box appears, that notifies that the document can't be removed, because it used by the task.

The behavior should be the same in both cases. I think, the behavior in the first scenario is better.