Annotations widget is added several times in to the BLAST dialog

Scenario to reproduce:

1. Select the "Tools" -> "BLAST" -> "BLAST Search..." item in the main menu.
   Expected state: there is a "Request to Local BLAST Database" dialog without an annotation widget.
2. Set any input sequence.
   Expected state: an annotation widget was added.
3. Set any another input sequence.
   Expected state: there is a single annotation widget.
   Current state: a new annotation widget is added atop the previous one. If you set the input sequence again, you'll receive the third widget.