Cycles / RNG:
* Avoid call to empty path_rng_end() function when using __SOBOL__. Maybe the compiler optimizes that out already, but adding a check here does not harm.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56691 954f8c5b-7b00-dc11-b283-0030488c597c