parameters: convert action has no history

  1. select a parameter in parameters panel,
  2. right-click, convert to what ever type
  3. control - z,
  4. there is not history as expected

Can’t reproduce it here. I have a history as expected after press CTRL-z.
What I have is that the CTRL-z triggers two times the undo action. THis has been reported by Zelgadis on pivotal tracker and I know exactly why does it happen.
I’ll try to fix it.