Bug 11587: get rid of warnings generated by IsSuperLibrarian with anonymous sessions

This corrects line 1250 of C4/Context.pm to be:
    return ($userenv->{flags}//0) % 2;
And thus avoids an uninitialized value used in the modulus.

TEST PLAN
---------
1) Apply the first patch (to update t/Context.t)
2) prove -v t/Context.t
-- This should fail tests 7 and 8
3) Apply this patch (to fix C4/Context.pm)
4) prove -v t/Context.t
-- All tests should succeed

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>

C4/Context.pm

@@ -1251,7 +1251,7 @@ sub IsSuperLibrarian {
         return 1;
     }
 
-    return $userenv->{flags} % 2;
+    return ($userenv->{flags}//0) % 2;
 }
 
 1;