message: Remove unnecessary quotes from shader
diff: @@ -407,7 +407,7 @@ void applyRefraction(const PixelParams pixel,
  #elif REFRACTION_TYPE == REFRACTION_TYPE_THIN
  refractionThinSphere(pixel, n0, -shading_view, ray);
  #else
  -#error "invalid REFRACTION_TYPE"
  +#error invalid REFRACTION_TYPE
  #endif
  /* compute transmission T */
  