[pitivi] transitions: don't activate when audio transition.

[Mathieu Duponchelle <mathieudu src gnome org>]

commit 752966e3b903e0628d9bd4a6a86d7582cd8f8d3c
Author: Mathieu Duponchelle <mathieu duponchelle opencreed com>
Date:   Sun Nov 30 06:16:02 2014 +0100

    transitions: don't activate when audio transition.
    
    + remove unused imports

 pitivi/transitions.py |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/pitivi/transitions.py b/pitivi/transitions.py
index 280892c..1d09984 100644
--- a/pitivi/transitions.py
+++ b/pitivi/transitions.py
@@ -22,10 +22,8 @@
 
 import os
 
-from gi.repository import Gst
 from gi.repository import GES
 from gi.repository import GLib
-from gi.repository import GObject
 from gi.repository import Gtk
 from gi.repository import GdkPixbuf
 
@@ -282,6 +280,8 @@ class TransitionsListWidget(Gtk.VBox, Loggable):
         """
         Hide the infobar and show the transitions UI.
         """
+        if isinstance(element, GES.AudioTransition):
+            return
         self.element = element
         self.element.connect("notify::border", self._borderChangedCb)
         self.element.connect("notify::invert", self._invertChangedCb)