[pitivi] Fix keyframe removal. Fixes #587333.

[Edward Hervey <edwardrv src gnome org>]

commit 1966b4848ba6ccab283177f4fb1499b5e8d6efed
Author: Alessandro Decina <alessandro d gmail com>
Date:   Tue Jun 30 11:38:49 2009 +0200

    Fix keyframe removal. Fixes #587333.

 pitivi/ui/curve.py |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/pitivi/ui/curve.py b/pitivi/ui/curve.py
index a7ebcbc..83ca153 100644
--- a/pitivi/ui/curve.py
+++ b/pitivi/ui/curve.py
@@ -80,11 +80,12 @@ class Curve(goocanvas.ItemSimple, goocanvas.Item, View, Zoomable):
 
         def double_click(self, pos):
             interpolator = self._view.interpolator
-            if not self._kf:
+            kf = self._view.findKeyframe(pos)
+            if kf is None:
                 time, value = self.xyToTimeValue(pos)
                 interpolator.newKeyFrame(time, value)
             else:
-                self._view.interpolator.removeKeyFrame(self._kf)
+                self._view.interpolator.removeKeyFrame(kf)
 
         def xyToTimeValue(self, pos):
             bounds = self._view.bounds