Add clamp to zero in SampleFourier
Add clamp to zero in SampleFourier

Guard against trying to take sqrt of a very small negative number.

mmp/pbrt-v3,ambakshi/pbrt-v3,nispaur/pbrt-v3,nispaur/pbrt-v3,bssrdf/pbrt-v3,mmp/pbrt-v3,bssrdf/pbrt-v3,nyue/pbrt-v3,ambakshi/pbrt-v3,nyue/pbrt-v3,mmp/pbrt-v3,shihchinw/pbrt-v3,nyue/pbrt-v3,nispaur/pbrt-v3,nyue/pbrt-v3,ambakshi/pbrt-v3,shihchinw/pbrt-v3,shihchinw/pbrt-v3,bssrdf/pbrt-v3,nispaur/pbrt-v3,mmp/pbrt-v3,shihchinw/pbrt-v3