Calendar Beta 3: "An unexpected error occurred. Please try again later."

I updated from Beta 1 to Beta 3 directly. Now, any time I open the Calendar page it shows a white page with just "An unexpected error occurred. Please try again later." on it...
 
Code:
Error Info
Class 'NixFifty_GiftUpgrades_NixFifty_Calendar_ControllerPublic_Calendar' not found - library/XenForo/FrontController.php:463

Stack Trace
#0 /Applications/XAMPP/xamppfiles/htdocs/forum/library/XenForo/FrontController.php(343): XenForo_FrontController->_getValidatedController('NixFifty_Calend...', 'Index', Object(XenForo_RouteMatch))
#1 /Applications/XAMPP/xamppfiles/htdocs/forum/library/XenForo/FrontController.php(134): XenForo_FrontController->dispatch(Object(XenForo_RouteMatch))
#2 /Applications/XAMPP/xamppfiles/htdocs/forum/index.php(13): XenForo_FrontController->run()
#3 {main}

Request State
Array
(
    [url] => http://localhost/forum/calendar/
    [_GET] => Array
        (
        )

    [_POST] => Array
        (
        )

)
 
What version of Gift Upgrades are you using? I'm not getting this in either production or development environments.
 
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