Crash on the second search

Scenario:

1. Open sequence, open the "PCR primer design..." tab.
2. Set "Melting point" minimum value to 54 and click "Start".
   Expected: one region was found and shown in the table, the annotation was created.
3. Set "Melting point" minimum value to 51.
   Expected: five regions were found and shown in the table, five annotations were created.
   Current: five regions were found, but there are the only one in the table and four empty rows.
4. Click on an empty row.
   Current: crash.