[pitivi] previewers: Fix initial value of AudioPreviewer.lastUpdate

[Thibault Saunier <tsaunier src gnome org>]

commit 67b9d5ca04549f50674548e1bf0c501b78730a7f
Author: Alexandru Băluț <alexandru balut gmail com>
Date:   Wed Apr 30 06:00:29 2014 +0200

    previewers: Fix initial value of AudioPreviewer.lastUpdate

 pitivi/timeline/previewers.py |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/pitivi/timeline/previewers.py b/pitivi/timeline/previewers.py
index 302faf6..ffffb29 100644
--- a/pitivi/timeline/previewers.py
+++ b/pitivi/timeline/previewers.py
@@ -756,7 +756,7 @@ class AudioPreviewer(Clutter.Actor, PreviewGenerator, Zoomable, Loggable):
         self.set_content(self.canvas)
         self.width = 0
         self._num_failures = 0
-        self.lastUpdate = datetime.now()
+        self.lastUpdate = None
 
         self.current_geometry = (-1, -1)
 
@@ -811,7 +811,8 @@ class AudioPreviewer(Clutter.Actor, PreviewGenerator, Zoomable, Loggable):
     def _maybeUpdate(self):
         if self.discovered:
             self.log('Checking if the waveform for "%s" needs to be redrawn' % self._uri)
-            if datetime.now() - self.lastUpdate > WAVEFORM_UPDATE_INTERVAL:
+            if self.lastUpdate is None or datetime.now() - self.lastUpdate > WAVEFORM_UPDATE_INTERVAL:
+                # Last update was long ago or never.
                 self.lastUpdate = datetime.now()
                 self._compute_geometry()
             else: