[Mac, crash] NCBI Blast spam

Reproducible on 49 prerelease. Possibly reproducible on other OS.

1. Open data/samples/MMDB/1CRN.prt
   Expected: the SV appears.
2. Run RemoteBLASTTask ~15 times:
   1. click "Query NCBI BLAST database" on the toolbar,
      expected: the "Search Through a Remote Database" dialog appears;
   2. set Search timeout=60 min;
   3. press Enter,
      expected: the "RemoteBLASTTask" task has started;
   4. repeat the specified number of times.
      Expected: the tasks completed successfully, all found annotation are displayed, no redundant messages/notifications.
      Current state:
      1. crash after ~20 mins,
      2. last message in the UGENE log: QEventDispatcherUNIXPrivate(): Cannot continue without a thread pipe,
      3. last message in Terminal: QThreadPipe: Unable to create pipe: Too many open files.