Fix harmless use of unintialized memory

Still nbice to avoid such access to keep valgrind output more sane.

source/blender/blenkernel/intern/shrinkwrap.c

@@ -357,7 +357,7 @@ static void shrinkwrap_calc_normal_projection_cb_ex(
 	/* don't set the initial dist (which is more efficient),
 	 * because its calculated in the targets space, we want the dist in our own space */
 	if (proj_limit_squared != 0.0f) {
-		if (len_squared_v3v3(hit->co, co) > proj_limit_squared) {
+		if (hit->index != -1 && len_squared_v3v3(hit->co, co) > proj_limit_squared) {
 			hit->index = -1;
 		}
 	}