[pitivi] Fix a traceback seeking in an empty timeline. Fixes #594311.

[Edward Hervey <edwardrv src gnome org>]

commit 832ca6470f1a8fbf31e875b78f470335449a5c9b
Author: Alessandro Decina <alessandro d gmail com>
Date:   Mon Sep 7 11:51:51 2009 +0200

    Fix a traceback seeking in an empty timeline. Fixes #594311.

 pitivi/ui/ruler.py |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/pitivi/ui/ruler.py b/pitivi/ui/ruler.py
index 2dd872a..0cfb8fb 100644
--- a/pitivi/ui/ruler.py
+++ b/pitivi/ui/ruler.py
@@ -169,7 +169,7 @@ class ScaleRuler(gtk.Layout, Zoomable, Loggable):
     def _seekerSeekCb(self, seeker, position, format):
         # clamping values within acceptable range
         duration = self.getShadedDuration()
-        if duration == gst.CLOCK_TIME_NONE:
+        if duration in (0, gst.CLOCK_TIME_NONE):
             return
         if position > duration:
             position = duration - (1 * gst.MSECOND)