Fix thread no-stop bug

src/device/DeviceManager.cpp

@@ -300,3 +300,8 @@ void DeviceManager::processScan(const char* json, bool empty) {
 	THROW_ERROR(errmsg);
 	qDebug() << ">>>>>>>>>>>>>>>>>>>>>ScanControl failed";
 }
+
+void DeviceManager::close() {
+    previewDataCaller->terminate();
+    delete previewDataCaller;
+}

src/device/DeviceManager.h

@@ -16,6 +16,7 @@ public:
         return &manager;
     }
     void initDevice();
+	void close();
     void setErrorOccurred(bool v){
         errorOccurred = v;
     }
@@ -35,7 +36,7 @@ private:
 	int deviceInfTimerID = -1;
 	int lastStatus = -1;
 	bool previewing = false;
-	bool endLoop = false;
+	volatile bool endLoop = false;
 	bool errorOccurred = false;
 	QThread* previewDataCaller;
 };

src/systemsettingform.cpp

@@ -157,8 +157,10 @@ systemSettingForm::systemSettingForm(QWidget* parent) :
 
 systemSettingForm::~systemSettingForm()
 {
-	diskInfoCaller->quit();
-	diskInfoCaller->wait();
+    diskInfoCaller->terminate();
+//	diskInfoCaller->quit();
+//	diskInfoCaller->wait();
+    delete diskInfoCaller;
 }
 
 void systemSettingForm::updateStorageUsed()