set NULL to m_serverthread in the constructor

src/controllers/stereo_watchdog/StereoWatchdogController.cpp

@@ -53,6 +53,8 @@ StereoWatchdogController::StereoWatchdogController(const string& name) :Experime
 	m_Level2Driver.init(this, "level2driver");
 	registerFunction(TYPE);
 
+	m_serverThread = NULL;
+
 
 }
 
@@ -77,8 +79,10 @@ StereoWatchdogController::StereoWatchdogController(const StereoWatchdogControlle
  * Destructor
  */
 StereoWatchdogController::~StereoWatchdogController() {
-	m_serverThread->join();
-	delete m_serverThread;
+	if (m_serverThread != NULL) {
+		m_serverThread->join();
+		delete m_serverThread;
+	}
 }