Fix #8819 sorting

@PVince81 Took me a while cause I had a lot to learn, better have a good look :)
I find it a bit strange to have the small point of the triangle pointing upwards when the biggest files are on top, however you see both being used so I left them like they were.

Comments are welcome.

Please document this new attribute in the comment above, it is not clear what it is needed for.