[pitivi] Some more fixes for #584135.

[Edward Hervey <edwardrv src gnome org>]

commit 9853b5cdeab9ebd05cbcc583969ae1c685ff20f6
Author: Alessandro Decina <alessandro d gmail com>
Date:   Sun Feb 21 13:40:52 2010 +0100

    Some more fixes for #584135.

 pitivi/ui/encodingdialog.py |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/pitivi/ui/encodingdialog.py b/pitivi/ui/encodingdialog.py
index 2a42926..ac14bd7 100644
--- a/pitivi/ui/encodingdialog.py
+++ b/pitivi/ui/encodingdialog.py
@@ -182,8 +182,11 @@ class EncodingDialog(GladeWindow, Loggable):
         self.have_audio = False
 
         # we can only render TimelineSourceFactory
-        timeline_source = self.pipeline.factories.keys()[0]
+        sources = [factory for factory in self.pipeline.factories.keys()
+                if isinstance(factory, SourceFactory)]
+        timeline_source = sources[0]
         assert isinstance(timeline_source, TimelineSourceFactory)
+
         for track in timeline_source.timeline.tracks:
             if isinstance(track.stream, AudioStream) and track.duration > 0:
                 self.have_audio = True