Optimize the full rescan path a bit, and add a check for safety (that should be a noop)

src/musicscanner.cpp

@@ -261,6 +261,8 @@ MusicScanner::listerFinished( const QMap<QString, unsigned int>& newmtimes  )
         m_filesToDelete << m_filemtimes[ key ].keys().first();
     }
     commitBatch( m_scannedfiles, m_filesToDelete );
+    m_scannedfiles.clear();
+    m_filesToDelete.clear();
     
     // remove obsolete / stale files
     foreach ( const QString& path, m_dirmtimes.keys() )

src/scanmanager.cpp

@@ -168,6 +168,7 @@ ScanManager::filesDeleted( const QStringList& files, const Tomahawk::collection_
 {
     Q_UNUSED( files );
     Q_UNUSED( collection );
+    if ( !TomahawkSettings::instance()->scannerPaths().isEmpty() )
         runDirScan( TomahawkSettings::instance()->scannerPaths(), true );
 }