lib/selection*: trivial undefined-behavior fix

lib/selection_iter.c

@@ -240,7 +240,7 @@ void iter_choose_transport(struct kr_query *qry, struct kr_transport **transport
 
 	unpack_state_from_zonecut(local_state, qry);
 
-	struct choice choices[trie_weight(local_state->addresses)];
+	struct choice choices[trie_weight(local_state->addresses) + 1/*avoid 0*/];
 	/* We may try to resolve A and AAAA record for each name, so therefore
 	 * 2*trie_weight(…) is here. */
 	struct to_resolve resolvable[2 * trie_weight(local_state->names)];