[gnome-builder] libide: ensure we have items to merge before dereferencing

[Christian Hergert <chergert src gnome org>]

commit d4e8f9687f7b8c211a8c5d46afc76f7047348919
Author: Christian Hergert <christian hergert me>
Date:   Mon Mar 23 22:13:09 2015 -0700

    libide: ensure we have items to merge before dereferencing

 libide/ide-back-forward-list.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/libide/ide-back-forward-list.c b/libide/ide-back-forward-list.c
index 20b00c9..4a7edd1 100644
--- a/libide/ide-back-forward-list.c
+++ b/libide/ide-back-forward-list.c
@@ -309,6 +309,12 @@ ide_back_forward_list_merge (IdeBackForwardList *self,
   ar1 = ide_back_forward_list_to_array (self);
   ar2 = ide_back_forward_list_to_array (branch);
 
+  g_assert (ar1 != NULL);
+  g_assert (ar2 != NULL);
+
+  if (ar2->len == 0)
+    return;
+
   first = g_ptr_array_index (ar2, 0);
 
   for (i = 0; i < ar1->len; i++)