[gnome-builder] highlighting: ensure buffer was cleared from unbind signal

[Christian Hergert <chergert src gnome org>]

commit b7a41eb5de436ed4dc7b75d574cd1f4966ddbf77
Author: Christian Hergert <chergert redhat com>
Date:   Wed Jan 3 19:39:32 2018 -0800

    highlighting: ensure buffer was cleared from unbind signal

 src/libide/highlighting/ide-highlight-engine.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/src/libide/highlighting/ide-highlight-engine.c b/src/libide/highlighting/ide-highlight-engine.c
index 9a70b63..deed432 100644
--- a/src/libide/highlighting/ide-highlight-engine.c
+++ b/src/libide/highlighting/ide-highlight-engine.c
@@ -805,6 +805,8 @@ ide_highlight_engine_dispose (GObject *object)
   g_clear_object (&self->highlighter);
   g_clear_object (&self->settings);
 
+  g_assert (self->buffer == NULL);
+
   G_OBJECT_CLASS (ide_highlight_engine_parent_class)->dispose (object);
 }