When trying to rename page A to page B, and the page B already exists and that we check the checkbox "Yes, delete the page", we get Fatal exception of type "MWException". We have to manually delete page B to be able to rename page A.
Some vandals/LTA are exploiting this bug to annoy and waste admins' time, please fix.

Steps to reproduce the bug:

1. Try to rename page A to a title of a page that already exists (let's call it "page B") and click "Move page"
2. MediaWiki tells you that "The destination page B already exists. Do you want to delete it to make way for the move?"
3. Check the checkbox "Yes, delete the page" and click "Move page"

Expected result
Page B deleted and page A moved with the title of page B.

Actual Result
Fatal exception of type "MWException"