[gnome-builder] highlight: fix leak of buffer instance

[Christian Hergert <chergert src gnome org>]

commit 60840c174b5015757801cfa194fea0552d7768ad
Author: Christian Hergert <chergert redhat com>
Date:   Mon May 28 17:45:29 2018 -0700

    highlight: fix leak of buffer instance

 src/libide/highlighting/ide-highlight-engine.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/libide/highlighting/ide-highlight-engine.c b/src/libide/highlighting/ide-highlight-engine.c
index 22ba8bb2b..e4ec31e8f 100644
--- a/src/libide/highlighting/ide-highlight-engine.c
+++ b/src/libide/highlighting/ide-highlight-engine.c
@@ -311,7 +311,7 @@ ide_highlight_engine_apply_style (const GtkTextIter *begin,
 static gboolean
 ide_highlight_engine_tick (IdeHighlightEngine *self)
 {
-  GtkTextBuffer *buffer;
+  g_autoptr(GtkTextBuffer) buffer = NULL;
   GtkTextIter iter;
   GtkTextIter invalid_begin;
   GtkTextIter invalid_end;