fix for inserting a color-curve point.
- was reading outside memory bounds checking the 'x' point.
- inserting a point to the right of the last point would add a point to the very left instead.


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56367 954f8c5b-7b00-dc11-b283-0030488c597c