Android: flush the current video frame when the video output is reset.

The texture renderer could end up in a situation where a frame could be
scheduled to be rendered after the renderer was reset.

Change-Id: Ie6b6c9d0b5f5851f14aa6eb5f8421196aff8c691
Reviewed-by: Christian Stromme <christian.stromme@qt.io>

src/plugins/android/src/common/qandroidvideooutput.cpp

@@ -284,6 +284,10 @@ void QAndroidTextureVideoOutput::stop()
 
 void QAndroidTextureVideoOutput::reset()
 {
+    // flush pending frame
+    if (m_surface)
+        m_surface->present(QVideoFrame());
+
     clearSurfaceTexture();
 }