Bug 23771: Don't look for patrons if we don't have a userid

Bug 23771: Don't look for patrons if we don't have a userid

While the code requires external auth to test, the change is simple enough I
think a good read would suffice

To test:
1 - You either need Shib or CAS enabled and setup
2 - Add two users with blank.null cardnumbers
3 - Lock those user accounts
    Set failedloginattempts to 1
    Try a bad login with the userid
    Or set via the DB
4 - Try a good login via the external auth
5 - Note it fails
6 - Apply patch
7 - Login now succeeds

Signed-off-by: Mike Somers - Bridgewater State University <msomers@bridgew.edu>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit c9c6dd10167bc4c60cb384651f4dc802944c4228)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>