[pinpoint] Check that pp_slidep is set before dereferencing it

[Emmanuele Bassi <ebassi src gnome org>]

commit bbca5f7b0c695b70e971e19bfb2e6c9ee94cdb09
Author: Emmanuele Bassi <ebassi linux intel com>
Date:   Thu Aug 4 11:23:25 2011 +0100

    Check that pp_slidep is set before dereferencing it

 pp-clutter.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/pp-clutter.c b/pp-clutter.c
index 3fe955a..8ae18ef 100644
--- a/pp-clutter.c
+++ b/pp-clutter.c
@@ -1511,6 +1511,10 @@ static gboolean update_speaker_screen (ClutterRenderer *renderer)
   PinPointPoint *point;
   int n_slides;
   int slide_no;
+
+  if (!pp_slidep)
+    return FALSE;
+
   point = pp_slidep->data;
   static float current_slide_time = 0.0;
   static float current_slide_duration = 0.0;