The first error message:
ErrorException: Undefined index: location - library/XenForo/ControllerPublic/Register.php:783
Stack Trace:
#0 /home/lwl/public_html/library/XenForo/ControllerPublic/Register.php(783): XenForo_Application::handlePhpError(8, 'Undefined index...', '/home/lwl/publi...', 783...