Fix buffer-overflow in lattice deform evaluation

Caused Victor.blend from the cloud to crash with ASan. Four floats are
fetched from the stack, but the buffer was only three wide.

Caused by 042143440d. Issue was probably harmless since the fourth
element wasn't actually touched.

source/blender/blenkernel/intern/lattice_deform.c

@@ -169,7 +169,7 @@ void BKE_lattice_deform_data_eval_co(LatticeDeformData *lattice_deform_data,
   int ui, vi, wi, uu, vv, ww;
 
   /* vgroup influence */
-  float co_prev[3], weight_blend = 0.0f;
+  float co_prev[4] = {0}, weight_blend = 0.0f;
   copy_v3_v3(co_prev, co);
 #ifdef __SSE2__
   __m128 co_vec = _mm_loadu_ps(co_prev);