* #6326 : don't destroy preview widget more than one time

sflphone-common/src/dbus/configurationmanager.cpp

@@ -984,10 +984,12 @@ void ConfigurationManager::startVideoPreview(const int32_t &width, const int32_t
 
 void ConfigurationManager::stopVideoPreview()
 {
+	if (preview_.get()) {
 		_debug("Stopping video preview");
 		preview_->stop();
 		preview_.reset();
 		// notify client via dbus
 		videoStopped();
 	}
+}