civicrm_member_roles_sync_user breaks with Drupal membership-based integration

The following function references the variable $op which is undefined, and causes an E_NOTICE warning to be shown to end users. My fix was to remove the if condition entirely, but not knowing the intended functionality, I haven't attached a patch.

File: sites/all/modules/civicrm/drupal/modules/civicrm_member_roles/civicrm_member_roles.module

function civicrm_member_roles_sync_user( $account)
{
if ( ! civicrm_initialize( ) )

{ return; }

if ( variable_get('civicrm_member_roles_sync_method', 0) == 0)

{ _civicrm_member_roles_sync($account->uid); }

if (variable_get('civicrm_member_roles_sync_method', 0) == 3) {
if ($op == 'insert')

{ _civicrm_member_roles_sync($account->uid); }

}
}