Bug 1995527: Need to check module is installed before deleting content

When deleting a page or collection

Which can happen when deleting
- a group
- a user

etc

Change-Id: I25889d71295bd3741c8479beb69c4746541a8dfd
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>
(cherry picked from commit eded804f)