Upgrade Wizard "migrateFeloginPlugins" fails if empty pi_flexform

[kanow]

Upgrade wizard fails if pi_flexform field is empty.
I don't know why these field are empty on some plugins but they are there ;-).
With such kind of plugins the wizard fails with error message:

[ERROR] <error>Something went wrong while running Migrate felogin plugins to use prefixed flexform keys</error>

Maybe wizard should be check the not empty pi_flexform field?

$statement = $queryBuilder->select('uid')
            ->addSelect('pi_flexform')
            ->from('tt_content')
            ->where(
                $queryBuilder->expr()->eq('CType', $queryBuilder->createNamedParameter('login')),
                $queryBuilder->expr()->neq('pi_flexform', $queryBuilder->createNamedParameter('', Connection::PARAM_STR))
            )
            ->executeQuery();

Found this on running wizards in upgrade of TYPO3 from 7.6 to 13.4 ;-)

Maybe a short message above the success message that some elements are not migrated is helpful.