FIX: Divisoin by zero / NaN issue with slider where the thumb would end up never getting a correct position.  Thanks to Erik Hjortsberg.
FIX: Divisoin by zero / NaN issue with slider where the thumb would end up never getting a correct position.  Thanks to Erik Hjortsberg.

--HG--
branch : v0-7

cbeck88/cegui-mirror-two,cbeck88/cegui-mirror-two,cbeck88/cegui-mirror-two,cbeck88/cegui-mirror-two,cbeck88/cegui-mirror-two