Cannot "undo" rename of a page if the "redirect" option was chosen on the first rename

Steps to reproduce:

• create a page called "TestPage"
• rename it to "Test Page" (with a space between the words) with all default options - including "redirect" option checked
• I would like to "undo" this rename so I go on the renamed page "Test Page"
• I try to rename it back to "TestPage"

Actual result:

• An error will be displayed, saying that a document already exists with that name and that a new document name should be chosen
• However, on the homepage of the wiki, in the Pages tree, I see no page with the name "TestPage", only the "Test Page" one that I am actually trying to rename

Expected result:

• I should have a solution out of this situation: either be able to rename back to the initial name with no warning ("undo" the previous rename), or to be able to delete the "already existing page" so that I can rename. The situation should "make sense", which it does not really...