Fix Cycles crash in certain hair configurations

The issue was caused by hair shader setup setting normal to a non
finite value, which then gets used to create a ray with non-finite
direction, making BVH traversal to run out of stack memory.

Happens with 150_0040_A.lighting.blend frame 112 of the Sprites
project.

Differential Revision: https://developer.blender.org/D12692

intern/cycles/kernel/geom/geom_curve_intersect.h

@@ -713,7 +713,7 @@ ccl_device_inline void curve_shader_setup(const KernelGlobals *kg,
 
     P = transform_point(&tfm, P);
     D = transform_direction(&tfm, D * t);
-    D = normalize_len(D, &t);
+    D = safe_normalize_len(D, &t);
   }
 
   int prim = kernel_tex_fetch(__prim_index, isect_prim);