Bug 22370: Prevent OPAC users from seeing staff news from URL

Bug 22370: Prevent OPAC users from seeing staff news from URL

To test:
1) Have some OPAC and staff only news items
2) On the OPAC view a single news item
3) Change the ID in the URL to the ID of a staff news item
4) Notice you can view the news item without any problems
5) Apply the patch and refresh the page
6) An error should show that the news item doesn't exist
7) Confirm you can still view OPAC news items individually

Sponsored-by: Catalyst IT
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>