Image upload slider not moving

[ninetailz]

While testing beta and uploading image i noticed this,
The slider on the preview wasn't moving, only one progress bar was moving

This was on version 4.0-beta1-20140713

[jdgrimes]

I have also experienced this on my local installs, and also on some live sites running 3.9.1. The sliders don't move.

[pavelevap]

Yes, same problem with latest trunk.

[wonderboymusic]

Fixed in [29609] - and probably other places