1414: Scrollbar grabber bug [#8213]

[Dreadlau]

In skinned mode
select a skin which has a graphic for the scrollbar grabber.
Select a node containing a lot of songs enough to make the slider of the "tracklist scrollbar" smaller than the grabber.
Note that the grabber is still displaying!

The grabber is supposed to be hided when the slider becomes too small.
Like it works in unskinned mode.

Tested on windows7

[PetrCBR]

Tracked as 8213.