Error using RNG with Conditional Fields

[e-Mole]

I need to hide certain fields according to the user's choice (on the Event registration form). So I use the Conditional Fields module (last DEV version). Content forms - Page, Article, ... works as they do. However, if the condition (in Conditional Fields settings) for the registration form is added, the condition settings dialog will not be displayed. Action ends with error:

Recoverable fatal error: Argument 1 passed to Drupal\rng\EventManager::getMeta() must implement interface Drupal\Core\Entity\EntityInterface, null given, called in /var/www/public_html/modules/rng/src/Form/RegistrationForm.php on line 62 and defined in Drupal\rng\EventManager->getMeta() (line 45 of modules/rng/src/EventManager.php).

In Drupal 8, I'm not able to find the error. Please help with removing this error.

Thanks for great module!