tree data BUGFIX inserting nodes before opaq nodes

Author: michalvasko

src/tree_data.c

@@ -672,7 +672,7 @@ lyd_insert_node(struct lyd_node *parent, struct lyd_node **first_sibling_p, stru
         anchor = lyd_insert_get_next_anchor(first_sibling, node);
 
         /* cannot insert data node after opaque nodes */
-        if (node->schema && first_sibling && !first_sibling->prev->schema) {
+        if (!anchor && node->schema && first_sibling && !first_sibling->prev->schema) {
             anchor = first_sibling->prev;
             while ((anchor != first_sibling) && !anchor->prev->schema) {
                 anchor = anchor->prev;