[gnome-builder] tree: add some missing precondition checks

[Christian Hergert <chergert src gnome org>]

commit 348bf82f5dad812c65df02cf77cc8300964d16bc
Author: Christian Hergert <christian hergert me>
Date:   Sat Apr 11 14:11:38 2015 -0700

    tree: add some missing precondition checks

 src/tree/gb-tree.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)
---
diff --git a/src/tree/gb-tree.c b/src/tree/gb-tree.c
index a7f9437..85da6ac 100644
--- a/src/tree/gb-tree.c
+++ b/src/tree/gb-tree.c
@@ -882,6 +882,10 @@ gb_tree_append (GbTree     *tree,
                 GbTreeNode *node,
                 GbTreeNode *child)
 {
+  g_return_if_fail (GB_IS_TREE (tree));
+  g_return_if_fail (GB_IS_TREE_NODE (node));
+  g_return_if_fail (GB_IS_TREE_NODE (child));
+
   gb_tree_add (tree, node, child, FALSE);
 }
 
@@ -898,6 +902,10 @@ gb_tree_prepend (GbTree     *tree,
                  GbTreeNode *node,
                  GbTreeNode *child)
 {
+  g_return_if_fail (GB_IS_TREE (tree));
+  g_return_if_fail (GB_IS_TREE_NODE (node));
+  g_return_if_fail (GB_IS_TREE_NODE (child));
+
   gb_tree_add (tree, node, child, TRUE);
 }