[pitivi] project: Check that the timeline could be extracted before using it

[Thibault Saunier <tsaunier src gnome org>]

commit 767969bea69f90d01bdd4a6222237ecdefebe044
Author: Thibault Saunier <thibault saunier collabora com>
Date:   Mon Jul 8 21:33:59 2013 -0400

    project: Check that the timeline could be extracted before using it

 pitivi/project.py |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/pitivi/project.py b/pitivi/project.py
index a8b770e..c67ccd7 100644
--- a/pitivi/project.py
+++ b/pitivi/project.py
@@ -812,10 +812,10 @@ class Project(Loggable, GES.Project):
         unlike GES.Project
         """
         self.timeline = self.extract()
-        self.timeline.set_auto_transition(True)
-        self._calculateNbLoadingAssets()
         if self.timeline is None:
             return False
+        self.timeline.set_auto_transition(True)
+        self._calculateNbLoadingAssets()
 
         self.timeline.selection = Selection()
         self.pipeline = Pipeline()