interval: fix ActorInterval endFrame assignment when passing duration

Fixes: #187

direct/src/interval/ActorInterval.py

@@ -83,7 +83,7 @@ class ActorInterval(Interval.Interval):
                 if startTime == None:
                     startTime = float(self.startFrame) / float(self.frameRate)
                 endTime = startTime + duration
-                self.endFrame = duration * self.frameRate
+                self.endFrame = endTime * self.frameRate
             else:
                 # No end frame specified.  Choose the maximum of all
                 # of the controls' numbers of frames.