qt: attempt fixing black screen

src/qt/qt_rendererstack.cpp

@@ -244,6 +244,7 @@ RendererStack::switchRenderer(Renderer renderer)
             createRenderer(renderer);
             disconnect(this, &RendererStack::blit, this, &RendererStack::blitDummy);
             blitDummied = false;
+            QTimer::singleShot(1000, this, [this] () { this->blitDummied = false; }; );
         });
 
         rendererWindow->hasBlitFunc() ? current.reset() : current.release()->deleteLater();