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>

Koha/Patron.pm

@@ -1092,6 +1092,7 @@ Return true if the patron (usually the logged in user) can see the patron's info
 
 sub can_see_patron_infos {
     my ( $self, $patron ) = @_;
+    return unless $patron;
     return $self->can_see_patrons_from( $patron->library->branchcode );
 }