Comment 2 for bug 512169

StacktraceTop:
 QMutex::lock (this=0xc0a090)
 Soprano::Virtuoso::QueryResultIteratorBackend::close
 ~Iterator (this=0x7f694800acf0)
 QHashData::free_helper (this=0xbbb9c0,
 Soprano::Server::ServerConnection::run (