Slider Thumb is having mouse over even if the mouse is not on it.

Steps to Reproduce:
---------------------
1) Run SwingSet2 demo and change the L&F to GTK. (Pass the gtkrc file path from the command line).
2) Go to Slider Demo.
3) Click on the Thumb of the Plain Slider. Now take the mouse out of the Thumb area. Note that the thumb has the mouse over effect color (You may not get this one in one go, but if u try it two three times u should get this).
4) Now take the mouse to some other slider and notice the mouse over effect.
5) This behaviour is shown only in the palin slider's thumb.
6) Please see tha attached image for more clearification

This I have tried with blueprint-0.8.7 engine.