Fix auth_ismanager calls in test cases

_test/cases/inc/auth_admincheck.test.php

@@ -19,11 +19,11 @@ class auth_admin_test extends UnitTestCase {
         $conf['manager'] = 'john,@managers,doe';
 
         // anonymous user
-        $this->assertEqual(auth_ismanager('jill', '',false), false);
+        $this->assertEqual(auth_ismanager('jill', null,false), false);
 
         // admin or manager users
-        $this->assertEqual(auth_ismanager('john', '',false), true);
-        $this->assertEqual(auth_ismanager('doe',  '',false), true);
+        $this->assertEqual(auth_ismanager('john', null,false), true);
+        $this->assertEqual(auth_ismanager('doe',  null,false), true);
 
         // admin or manager groups
         $this->assertEqual(auth_ismanager('jill', array('admin'),false), true);
@@ -35,11 +35,11 @@ class auth_admin_test extends UnitTestCase {
         $conf['superuser'] = 'john,@admin,doe,@roots';
 
         // anonymous user
-        $this->assertEqual(auth_ismanager('jill', '',true), false);
+        $this->assertEqual(auth_ismanager('jill', null,true), false);
 
         // admin user
-        $this->assertEqual(auth_ismanager('john', '',true), true);
-        $this->assertEqual(auth_ismanager('doe',  '',true), true);
+        $this->assertEqual(auth_ismanager('john', null,true), true);
+        $this->assertEqual(auth_ismanager('doe',  null,true), true);
 
         // admin groups
         $this->assertEqual(auth_ismanager('jill', array('admin'),true), true);