Header thumbnail isn't rendered according to configuration
The default configuration for header thumbnails of sys_file_reference records is
width: 50, height: 50c
which should result in a square image, where the height is cropped.
But the result is an image respecting aspect ratio.
This is due to the fact that the image processing was changed to IMAGE_PREVIEW, which only accepts
integer values as width and height and also only these two options.