Android: detect more error cases when rendering frames to textures.

Don't render the frame if the SurfaceTexture has been released or
if the render size is invalid.

Change-Id: I6b8bf14e023ff54a560b0a9e6027ef9d7d06ab6a
Reviewed-by: Christian Stromme <christian.stromme@theqtcompany.com>

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

@@ -304,6 +304,9 @@ void QAndroidTextureVideoOutput::renderFrameToFbo()
 {
     QMutexLocker locker(&m_mutex);
 
+    if (!m_nativeSize.isValid() || !m_surfaceTexture)
+        return;
+
     createGLResources();
 
     m_surfaceTexture->updateTexImage();