added a check to AbstractSlider._onThumbMouseMove() whether the main mouse button is still pressed; if that is not the case then the scrolling operation is stopped. for this, the DOM event must be checked because MouseEvent.isLeftButtonPressed() does not work for mousemove.
Issue 179
added a check to AbstractSlider._onThumbMouseMove() whether the main mouse button is still pressed; if that is not the case then the scrolling operation is stopped. for this, the DOM event must be checked because MouseEvent.isLeftButtonPressed() does not work for mousemove.