Fix SSO Auth test (#11155)

Because $dbuser is null here it causes PHP errors when using more strict modes.
So, just test that it is null.

tests/AuthSSOTest.php

@@ -133,9 +133,7 @@ class AuthSSOTest extends DBTestCase
 
         // Retrieve it and validate
         $dbuser = $a->getUser($a->getUserid($user));
-        $this->assertFalse($a->authSSOGetAttr(Config::get('sso.realname_attr')) === $dbuser['realname']);
-        $this->assertFalse($dbuser['level'] === "0");
-        $this->assertFalse($a->authSSOGetAttr(Config::get('sso.email_attr')) === $dbuser['email']);
+        $this->assertNull($dbuser);
     }
 
     // Excercise general auth flow with creation enabled