[pitivi] fix typos in factories

[Edward Hervey <edwardrv src gnome org>]

commit 3962b5f4fe3bf05221df154a6c6a6519ebc27bca
Author: Brandon Lewis <brandon_lewis berkeley edu>
Date:   Thu May 28 12:33:36 2009 -0700

    fix typos in factories

 pitivi/factories/file.py |   10 ++++++----
 pitivi/timeline/track.py |    5 +++--
 2 files changed, 9 insertions(+), 6 deletions(-)
---
diff --git a/pitivi/factories/file.py b/pitivi/factories/file.py
index 5f8ed6a..a131eff 100644
--- a/pitivi/factories/file.py
+++ b/pitivi/factories/file.py
@@ -27,7 +27,7 @@ import os
 from pitivi.factories.base import RandomAccessSourceFactory, \
         SinkFactory
 from pitivi.elements.imagefreeze import ImageFreeze
-from pitivi.stream import MultimediaStream
+from pitivi.stream import MultimediaStream, AudioStream, VideoStream
 
 class FileSourceFactory(RandomAccessSourceFactory):
     """
@@ -44,11 +44,13 @@ class FileSourceFactory(RandomAccessSourceFactory):
 
     def getInterpolatedProperties(self, stream):
         # FIXME: dummy implementation
-        props = RandomAccessSourceFactory.getInterpolatedProperties()
+        props = RandomAccessSourceFactory.getInterpolatedProperties(self, 
+            stream)
         if isinstance(stream, AudioStream):
-            return props.update({"volume" : (float, 0.5)})
+            props.update({"volume" : (float, 0.5)})
         elif isinstance(stream, VideoStream):
-            return props.update({"alpha" : (float, 0.5))
+            props.update({"alpha" : (float, 0.5)})
+        return props
 
 class PictureFileSourceFactory(FileSourceFactory):
     """
diff --git a/pitivi/timeline/track.py b/pitivi/timeline/track.py
index 5cd47a5..e935826 100644
--- a/pitivi/timeline/track.py
+++ b/pitivi/timeline/track.py
@@ -246,8 +246,9 @@ class TrackObject(Signallable):
         self._connectToSignals(obj)
 
         self._interpolators = {}
-        for prop in factory.getInterpolatedProperties(stream):
-            sef._interpolators[prop] = Interpolator(self, prop)
+        if stream:
+            for prop in factory.getInterpolatedProperties(stream):
+                sef._interpolators[prop] = Interpolator(self, prop)
 
     def release(self):
         self._disconnectFromSignals()