Fix an error when an anonymous user fills the form

SaveDBAction.execute method uses request.user for
form_user but request.user is not an instance of User for AnonymousUsers
therefore we need to check for whether the user is logged in or not

djangocms_form_builder/actions.py

@@ -119,7 +119,7 @@ def execute(self, form, request):
             keys = {}
             defaults = {
                 "form_name": get_option(form, "form_name"),
-                "form_user": request.user,
+                "form_user": request.user if get_option(form, "login_required", False) else None
             }
         defaults.update(
             {