Fix for bug #s 602 and 603.

When undoing not only should the capture state be checked to
see if it safe to undo, but the captured track should be
checked as well since some activities only set the captured
track and not the state.

src/TrackPanel.cpp

@@ -4164,7 +4164,7 @@ bool TrackPanel::IsDragZooming()
 /// Determines if the a modal tool is active
 bool TrackPanel::IsMouseCaptured()
 {
-   return (mMouseCapture != IsUncaptured);
+   return (mMouseCapture != IsUncaptured || mCapturedTrack != NULL);
 }