When an administrator attempts to remove a space's homepage, provide warning.

Problem Definition

Confluence administrators have the ability to remove a space's homepage via the Space Tools, which can cause many problems. One of which is that the new placeholder then does not display page tree in the left sidebar and can cause confusion, and not allowing the Page Tree to load in the New Look for Confluence.

Many other things can happen, involving stack trace errors showing in the GUI, etc.

Suggested Solution

1. Either we prevent a user from being able to do so,
2. or when the homepage is attempted to be removed, provide a warning about it.