Fix bug in DiffuseAreaLight::Pdf_Le() that caused NaNs
Fix bug in DiffuseAreaLight::Pdf_Le() that caused NaNs

It was passing the vector (0,0,0) for wo to the Interaction constructor, which now normalizes wo. This led to NaN values and hitting an assert in the debug build.

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