ensure we don't get a None in the host list

This can happen is a host is found but doesnt match any of the `hostnames` rules.

plugins/inventory/aws_ec2.py

@@ -751,8 +751,10 @@ def _add_hosts(self, hosts, group, hostnames, allow_duplicated_hosts=False):
         for host in hosts:
             if allow_duplicated_hosts:
                 hostname_list = self.get_all_hostnames(host, hostnames)
+            elif preferred_hostname := self._get_preferred_hostname(host, hostnames):
+                hostname_list = [preferred_hostname]
             else:
-                hostname_list = [self._get_preferred_hostname(host, hostnames)]
+                continue
 
             host = camel_dict_to_snake_dict(host, ignore_list=['Tags'])
             host['tags'] = boto3_tag_list_to_ansible_dict(host.get('tags', []))