[B4] ($timestamp) must be of type int, null

Hello,

I have 30+ of these errors since I upgrade from v4 to V5 beta 4 yesterday

TypeError: IPS\DateTime::ts(): Argument 
#1 ($timestamp) must be of type int, null given, called in /home/braca/vhosts/fmrte.com/applications/forums/applications/core/extensions/core/MemberFilter/Lastvisit.php on line 176 (0) 
#0 /home/braca/vhosts/fmrte.com/applications/forums/applications/core/extensions/core/MemberFilter/Lastvisit.php(176): IPS\DateTime::ts(NULL) 
#1 /home/braca/vhosts/fmrte.com/applications/forums/system/Member/GroupPromotion.php(337): IPS\core\extensions\core\MemberFilter\Lastvisit->matches(Object(IPS\Member), Array, Object(IPS\Member\GroupPromotion)) 
#2 /home/braca/vhosts/fmrte.com/applications/forums/system/Member/Member.php(4659): IPS\Member\GroupPromotion->matches(Object(IPS\Member)) 
#3 /home/braca/vhosts/fmrte.com/applications/forums/system/Member/Member.php(512): IPS\Member->checkGroupPromotion() 
#4 /home/braca/vhosts/fmrte.com/applications/forums/system/Login/Handler/OAuth2/OAuth2.php(530): IPS\Member->save() 
#5 /home/braca/vhosts/fmrte.com/applications/forums/system/Login/Handler/OAuth2/OAuth2.php(404): IPS\Login\Handler\OAuth2->_processAccessToken(Object(IPS\Login), Array) 
#6 /home/braca/vhosts/fmrte.com/applications/forums/system/Login/Handler/OAuth2/OAuth2.php(194): IPS\Login\Handler\OAuth2->_handleAuthorizationResponse(Object(IPS\Login)) 
#7 /home/braca/vhosts/fmrte.com/applications/forums/system/Login/Login.php(353): IPS\Login\Handler\OAuth2->authenticateButton(Object(IPS\Login)) 
#8 /home/braca/vhosts/fmrte.com/applications/forums/applications/core/modules/front/system/login.php(93): IPS\Login->authenticate() 
#9 /home/braca/vhosts/fmrte.com/applications/forums/system/Dispatcher/Controller.php(139): IPS\core\modules\front\system\login->manage() 
#10 /home/braca/vhosts/fmrte.com/applications/forums/system/Dispatcher/Dispatcher.php(169): IPS\Dispatcher\Controller->execute() 
#11 /home/braca/vhosts/fmrte.com/applications/forums/index.php(16): IPS\Dispatcher->run() 
#12 {main}

Thanks