Fix cycles AO issue, still was missing AO pass for black/non-diffuse objects.

intern/cycles/kernel/kernel_shader.h

@@ -619,6 +619,9 @@ __device float3 shader_bsdf_ao(KernelGlobals *kg, ShaderData *sd, float ao_facto
 		}
 	}
 
+	if(is_zero(*N))
+		*N = sd->N;
+	else
 		*N = normalize(*N);
 
 	return eval;