Merge pull request #373 from ilysenkov:bugfix_2440

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",

modules/highgui/test/test_gui.cpp

@@ -58,6 +58,9 @@ void Foo(int /*k*/, void* /*z*/) {}
 
 void CV_HighGuiOnlyGuiTest::run( int /*start_from */)
 {
+    ts->printf(ts->LOG, "GUI 0\n");
+    cvDestroyAllWindows();
+
     ts->printf(ts->LOG, "GUI 1\n");
     namedWindow("Win");