Ghost entries are leftover in the page tree when a page with underscore in name is deleted, if another page with a similar name exists

To reproduce:
Create a page subtree with the following structure (I created it under sandbox, but I guess it works on the root as well):

• a-b
  • test child page
• a_b

Delete the a_b page.

Expected result:
the page a_b disappears from the pages tree

Actual result:
the page a_b remains displayed in the page tree, clicking on it leads to a deleted page.