### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

It seems that it is possible to receive sns message in an sqs listener if there is a filterpolicy in place for null value in a message attribute, and a message is being sent without the message attribute.

### Expected Behavior

Don't recieve these type of messages

### How are you starting LocalStack?

With a docker-compose file

### Steps To Reproduce

`sns subscribe --topic-arn "demoTopicArn"  --protocol sqs --notification-endpoint "demoSqsEndpoint" --attributes '{"RawMessageDelivery": "true"}'`
`sns set-subscription-attributes --subscription-arn demoSubsArn --attribute-name FilterPolicy --attribute-value '{"testForNull": [null,{"anything-but": ["notgood"]}]}'`
`sns publish --topic-arn demoTopicArn --message "testforrecieval"`
`sqs receive-message --queue-url  "demoUrl"`

### Environment

```markdown
- OS: macOS 13.6
- LocalStack: 2.2.0
```


### Anything else?

_No response_
external_url = external_service_url("sns")
        unsubscribe_url = create_unsubscribe_url(external_url, subscriber["SubscriptionArn"])
        message_attributes = prepare_message_attributes(message_context.message_attributes)
        region_name = extract_region_from_arn(subscriber["SubscriptionArn"])
        event = {
            "Records": [
                {
                    "EventSource": "aws:sns",
                    "EventVersion": "1.0",
                    "EventSubscriptionArn": subscriber["SubscriptionArn"],
                    "Sns": {
                        "Type": message_context.type or "Notification",
                        "MessageId": message_context.message_id,
                        "TopicArn": subscriber["TopicArn"],
                        "Subject": message_context.subject,
                        "Message": message_context.message_content(subscriber["Protocol"]),
                        "Timestamp": timestamp_millis(),
                        "SignatureVersion": "1",
                        
                        
                        "Signature": "EXAMPLEpH+..",
                        "SigningCertUrl": f"https://sns.{region_name}.amazonaws.com/SimpleNotificationService-0000000000000000000000.pem",
                        "UnsubscribeUrl": unsubscribe_url,
                        "MessageAttributes": message_attributes,
                    },
                }
            ]
        }
        return json.dumps(event)
class SqsTopicPublisher(TopicPublisher):