Bug 22067: Return if no patron passed to can_see_patron_infos

Bug 22067: Return if no patron passed to can_see_patron_infos

To test:
1 - Find an adult patron
2 - Add a child to their account
3 - Delete the parent from the db
4 - Attempt to edit the child record
5 - Apply patch
6 - Repeat
7 - Note you can edit the child account
8 - Note guarantor id is not a link

Signed-off-by: Maryse Simard <maryse.simard@inlibro.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
No blocker for me, but we are a bit hiding that guarantorid probably should
be a foreign key cleared to NULL at deletion time.

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>