Fix T43596: Refraction BSDF crashes blender on pre-sse4 CPU

This is the same issue T43475: SSE4 code is more robust to non-finite values
in the ray origin/direction. So for now added a check before doing BVH traversal
for pre-SSE4 CPUs.

For sure actual root of the issue is a bit different and much more tricky to
solve, especially without disturbing render results too much. Still looking
into this.

In any case, it's kinda fine to have such a check, we might later make it to be
a kernel_assert() instead of just a return.

intern/cycles/kernel/geom/geom_triangle_intersect.h

@@ -314,9 +314,6 @@ ccl_device_inline float3 triangle_refine(KernelGlobals *kg,
 
 #ifdef __INTERSECTION_REFINE__
 	if(isect->object != OBJECT_NONE) {
-		if(UNLIKELY(t == 0.0f)) {
-			return P;
-		}
 #ifdef __OBJECT_MOTION__
 		Transform tfm = sd->ob_itfm;
 #else