[pitivi] Fix a traceback loading a project with no sources.

[Edward Hervey <edwardrv src gnome org>]

commit 2f5156e668e6c8551ebe18a74a7038cc3409b4e9
Author: Alessandro Decina <alessandro d gmail com>
Date:   Tue Aug 18 13:23:06 2009 +0200

    Fix a traceback loading a project with no sources.

 pitivi/formatters/etree.py |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/pitivi/formatters/etree.py b/pitivi/formatters/etree.py
index 9837229..d1200c4 100644
--- a/pitivi/formatters/etree.py
+++ b/pitivi/formatters/etree.py
@@ -618,6 +618,9 @@ class ElementTreeFormatter(Formatter):
         discoverer.connect("discovery-error", self._discovererDiscoveryErrorCb,
                 project, sources, uris, closure)
 
+        if not sources:
+            self._finishLoadingProject(project)
+            return
         # start the rediscovering from the first source
         source = sources[0]
         discoverer.addUri(source.uri)