Fixed cvDestroyAllWindows() without windows in QT (#2440)

diff --git a/modules/highgui/src/window_QT.cpp b/modules/highgui/src/window_QT.cpp
index d617e71..973b23c 100644 (file)
--- a/modules/highgui/src/window_QT.cpp
+++ b/modules/highgui/src/window_QT.cpp
@@ -499,7 +499,7 @@ CV_IMPL void cvDestroyWindow(const char* name)
 CV_IMPL void cvDestroyAllWindows()
 {
     if (!guiMainThread)
-        CV_Error( CV_StsNullPtr, "NULL guiReceiver (please create a window)" );
+        return;
 
     QMetaObject::invokeMethod(guiMainThread,
         "destroyAllWindow",