Fix possible crash when adding a tracker to a magnet torrent without metadata (Closes #1034254)

src/sessionapplication.h

@@ -54,6 +54,9 @@ public:
   SessionApplication(const QString &id, int &argc, char **argv);
   void commitData(QSessionManager & manager);
 
+protected:
+    virtual bool notify(QObject* receiver, QEvent* event);
+
   signals:
     void sessionIsShuttingDown();
 };