Error on custom login

I have a login form that works fine when the email/password is correct. But it throws an error when the password is wrong:

Quote

Error: Typed static property IPS\convert\Login::$_apps must not be accessed before initialization (0)
#0 C:\wamp64\www\50x\applications\convert\sources\Login.php(114): IPS\convert\Login->authenticatePasswordForMember(Object(IPS\Member), Object(class@anonymous))
#1 C:\wamp64\www\50x\system\Login\Login.php(286): IPS\convert\Login->authenticateUsernamePassword(Object(IPS\Login), 'atest@lajlajlaj...', Object(class@anonymous))
#2 C:\wamp64\www\50x\applications\linkedaccounts\extensions\core\AccountSettings\linkedAccounts.php(51): IPS\Login->authenticate()
#3 C:\wamp64\www\50x\applications\core\modules\front\system\settings.php(135): IPS\linkedaccounts\extensions\core\AccountSettings\linkedAccounts->getContent()
#4 C:\wamp64\www\50x\system\Dispatcher\Controller.php(139): IPS\core\modules\front\system\settings->manage()
#5 C:\wamp64\www\50x\applications\core\modules\front\system\settings.php(105): IPS\Dispatcher\Controller->execute()
#6 C:\wamp64\www\50x\system\Dispatcher\Dispatcher.php(169): IPS\core\modules\front\system\settings->execute()
#7 C:\wamp64\www\50x\index.php(16): IPS\Dispatcher->run()
#8 {main}

Backtrace:

Quote

#0 C:\wamp64\www\50x\init.php(827): IPS\Log::log('Error: Typed st...', 'uncaught_except...')
#1 [internal function]: IPS\IPS::exceptionHandler(Object(Error))
#2 {main}

If I set a NULL value to

	/**
	 *	@brief		Convert app cache
	 */
	protected static ?ActiveRecordIterator $_apps;

it works just fine. So the right would be:

	/**
	 *	@brief		Convert app cache
	 */
	protected static ?ActiveRecordIterator $_apps = NULL;

in applications / convert / sources / Login.php.