When deleting a page from a space that only contains WebPreferences, propose to delete children too

Several users have reported the following problem:

• They create a page (a Nested Page)
• They change the permissions (for example). Internally this creates a WebPreferences page (but they don't know about it, it's hidden)
• Then they delete the Nested Page. By default children are not deleted from the delete UI.
• Then they go to the Dashboard Tree and notice that the page is still listed (that's because WebPreferences is still there!)

Solution:

• On the delete page UI, if the page being deleted is not WebPreferences and if this space contains only the page being deleted + WebPreferences then automatically set the "delete children" checkbox to true.

I'm marking this issue as critical since a lot of users have asked this question.