Prevent admesh to reverse all facets twice in some mostly-random situations. Normalizing a null normal should still return a null normal in order to fix it properly later instead of treating it as if it was a true normal and thus reversing the facet (and if that is the first facet, all of the others would be reversed as well). #1362

xs/src/admesh/normals.c

@@ -359,7 +359,7 @@ void stl_normalize_vector(float v[])
   min_normal_length = 0.000000000001;
   if(length < min_normal_length)
     {
-      v[0] = 1.0;
+      v[0] = 0.0;
       v[1] = 0.0;
       v[2] = 0.0;
       return;