Tree view becomes too wide when alignment has been modified

Affected test:

• GUITest_common_scenarios_msa_editor_test_0077

Scenario:

1. Open "COI.aln".
2. Build a tree. Display it with the alignment.
3. Delete the first character of the first sequence.
4. Click the "Refresh tree" button on tree view toolbar.
   Current state: see the screenshot.