Errors after trying to create files content type only from the release tracker form

It was noticed by @oliviergoulet while doing a release that if he was trying to only create files from the Release Tracker form, a PHP error was happening.

Here is the error in the Drupal Logs:

TypeError: Drupal\eclipsefdn_packages\Form\ReleaseTrackerForm::updateFiles(): Argument #3 ($release) must be of type Drupal\eclipsefdn_packages\Entity\ReleaseNode, null given, called in /opt/drupal/web/modules/custom/eclipsefdn/eclipsefdn_packages/src/Form/ReleaseTrackerForm.php on line 185 in Drupal\eclipsefdn_packages\Form\ReleaseTrackerForm->updateFiles() (line 307 of /opt/drupal/web/modules/custom/eclipsefdn/eclipsefdn_packages/src/Form/ReleaseTrackerForm.php).

Note that this didn't prevent the form to create the necessary files it needed and didn't prevent the release to successfully take place.

But we should fix this issue so the form fail more gracefully.