[pitivi] viewer: Avoid using uninitialized local variable

[Alexandru Băluț <alexbalut src gnome org>]

commit 2e1f4760b4a2124bab4cbdbe0b9f425177b93325
Author: Alexandru Băluț <alexandru balut gmail com>
Date:   Sun Apr 9 01:15:03 2017 +0200

    viewer: Avoid using uninitialized local variable
    
    Used the same mechanism as in the undock method.
    
    Reviewed-by: Thibault Saunier <tsaunier gnome org>
    Differential Revision: https://phabricator.freedesktop.org/D1719

 pitivi/viewer/viewer.py |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/pitivi/viewer/viewer.py b/pitivi/viewer/viewer.py
index 5d57376..6561a8a 100644
--- a/pitivi/viewer/viewer.py
+++ b/pitivi/viewer/viewer.py
@@ -378,6 +378,7 @@ class ViewerContainer(Gtk.Box, Loggable):
         self.docked = True
         self.settings.viewerDocked = True
 
+        position = None
         if self.pipeline:
             position = self.pipeline.getPosition()
             self.pipeline.setState(Gst.State.NULL)
@@ -391,7 +392,7 @@ class ViewerContainer(Gtk.Box, Loggable):
         self.show()
 
         self.external_window.hide()
-        if position:
+        if self.pipeline:
             self.pipeline.pause()
             self.pipeline.simple_seek(position)