Set the webURL to nil for nil resources
Set the webURL to nil for nil resources

Delete the associated WebURL when a nil `Resource` is set on an ImageView.
This should prevent that the imageView is updated with the wrong image if a download previously started completes after the image is set again to nil.
Ashok28/Kingfisher,onevcat/Kingfisher,farice/VennCache,pNre/Kingfisher,tomaskraina/Kingfisher,farice/VennCache,Ashok28/Kingfisher,onevcat/Kingfisher,pNre/Kingfisher,pNre/Kingfisher,tomaskraina/Kingfisher,Ashok28/Kingfisher,farice/VennCache,tomaskraina/Kingfisher