Undoing transition causes a clip to be repeated

What steps will reproduce the problem?
Select two clips, create transition between them. Click undo multiple times to 
try to get back to the point before creating the transition.

What is the expected output? What do you see instead?
Expected output would be the transition clip to disappear and the two clips 
(from and to) be restored to what they were before creating the transition. 
What happens is that the second clip gets repeated multiple times and the 
transition does not disappear. However, the clips are restored, if I delete the 
transition and extra clip I get to the point where I was before.

What version of the product are you using? On what operating system?
0.12.0 tar.gz on ubuntu 14.04

Original issue reported on code.google.com by sampo.vu...@gmail.com on 13 Apr 2014 at 5:56

gcarranza / flowblade

Undoing transition causes a clip to be repeated #73