Don't allow a user to delete a space homepage without pointing them to set a new one

Problem: If a user deletes a page in a space that is the space homepage the following breaks:

• Clicking on the space homepage logo in the sidebar does nothing
• The navigation in the bottom left of the sidebar doesn't work

We don't want users to shoot themselves in the foot, what we propose is to not allow a user to delete a page if it is set as the homepage.

If they go to Tools > Delete and that is the homepage, instead of displaying a confirmation prompt we display:

"Oops, it looks like this page is set as your Space Homepage. You will need to <a href="link.to/viewspacesummary.action?key=spacekey>select another homepage</a> for your space before deleting this."

From the viewspacesummary.action they can set a new homepage.

That's it!