webform: The website encountered an unexpected error. - Invalid argument supplied for foreach()

Hello everyone.

I have these problems with the webform module:

1. When I click on “Settings” a white web page with this written appears:

The website encountered an unexpected error. Please try again later.
TypeError: Argument 2 passed to Drupal\webform\EntitySettings\WebformEntitySettingsBaseForm::appendDefaultValueToElementDescriptions() must be of the type array, null given, called in /home/piattafo/domains/piattaformapopper.net/public_html/modules/webform/src/EntitySettings/WebformEntitySettingsBaseForm.php on line 21 in Drupal\webform\EntitySettings\WebformEntitySettingsBaseForm->appendDefaultValueToElementDescriptions() (line 71 of modules/webform/src/EntitySettings/WebformEntitySettingsBaseForm.php).

2. In the back end of Drupal in the pages of webform this warning appears:

Warning: Invalid argument supplied for foreach() in Drupal\webform\WebformSubmissionForm->getWebformSetting() (line 2499 of modules/webform/src/WebformSubmissionForm.php).

What are the problems?

Thanks in advance to anyone will help me.