fx.collections: hashtable: add bounds checking to iterator

fx.collections/hashtable.c

@@ -623,6 +623,10 @@ static const fx_value *iterator_get_value(const fx_iterator *obj)
 	struct table_item *table = it->_h_p->t_items;
 	size_t capacity = primes[it->_h_p->t_max_index];
 
+	if (it->i >= capacity) {
+		return NULL;
+	}
+
 	if (table[it->i].i_item) {
 		return &it->item_value;
 	}