Fix SEGV in connect error for QT4.6

Fixes #80.

src/ComputrainerController.cpp

@@ -82,6 +82,7 @@ ComputrainerController::getRealtimeData(RealtimeData &rtData)
         msgBox.setIcon(QMessageBox::Critical);
         msgBox.exec();
         parent->Stop();
+        return;
     }
     // get latest telemetry
     myComputrainer->getTelemetry(Power, HeartRate, Cadence, Speed,