Undo Button Fountain Bug

I'm sure everybody experienced this already. You go back into the Fountain with low HP or Mana and bought an item, while you are still wounded. If you now klick the undo button at any time it will not only take the item, but also all the HP and Mana that you got after purchasing the item!

This is not such a big deal, but in a risky situation at your base, this can be crutial.

To recreate this bug just do a custom game with any champion and get some damage from an enemy tower. Go back to base and purchase an item before you are back to full HP. Hit the undo button next and you will see some hp going away again!