message: Added failsafe check to stochastic light sampling
  Added a check if the light list is > 0 when calculating the light selection probability
  for geometry lights.
diff: @@ -25,8 +25,12 @@ vec3f evaluateGeometryLights(const PathContext &pathContext,
  if (m != NULL && reduce_max(m->emission) > 0.f) {
  // at the moment we only support uniform light selection
  // therfore we can evaluate the selection PDF directly
  - const float lightSelectionPDF =
  + float lightSelectionPDF = 0.0f;
  + if(pathContext.numLights > 0)
  + {
  + lightSelectionPDF =
  (1.0f / (float)pathContext.numLights) * pathContext.numLightSamples;
  + }
  // convert pdf wrt. area to pdf wrt. solid angle
  const float cosd = dot(pathVertex.dg.Ng, ray.dir);
  const float lePdf = pathVertex.dg.areaPDF * sqr(ray.t) / abs(cosd);
  