Render Error when change the size of Window component while receiving sourceSizeChanged signal

When there is an Image item in a Window component, change the height and width of the Window in order to show the full image may result in an empty hole on the image.

The detail is here

It only occurs when the first image is opened in this way in a new Window. Any other images opened later won't have this problem.

 I set QSG_VISUALIZE=batches to check the render process. There is a hole indeed. Here is a gif. 

Only if the height and width both changed, this problem occurs. Change height or width when receiving SourceSizeChanged signal like the code provided in the link above won't cause this problem.