### 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_
assert sub_1_attrs["Attributes"]["PendingConfirmation"] == "false"
            # a
            sub_2_attrs = aws_client.sns.get_subscription_attributes(
                SubscriptionArn=sub_2["SubscriptionArn"]
            )
            assert sub_2_attrs["Attributes"]["PendingConfirmation"] == "true"
        finally:
            subscription_list = aws_client.sns.list_subscriptions_by_topic(TopicArn=topic_arn)
            for subscription in subscription_list["Subscriptions"]:
                aws_client.sns.unsubscribe(SubscriptionArn=subscription["SubscriptionArn"])
            for server in servers:
                server.stop()
    @markers.aws.manual_setup_required
    @pytest.mark.parametrize("raw_message_delivery", [True, False])
    def test_subscribe_external_http_endpoint(
        self, sns_create_http_endpoint, raw_message_delivery, aws_client, snapshot
    ):
        def _get_snapshot_requests_response(response: requests.Response) -> dict:
            parsed_xml_body = xmltodict.parse(response.content)
            for root_tag, fields in parsed_xml_body.items():
                fields.pop("@xmlns", None)
                if "ResponseMetadata" in fields:
                    fields["ResponseMetadata"]["HTTPHeaders"] = dict(response.headers)
                    fields["ResponseMetadata"]["HTTPStatusCode"] = response.status_code
            return parsed_xml_body
        snapshot.add_transformer(
            [
                snapshot.transform.key_value("RequestId"),
                snapshot.transform.key_value("Token"),
                snapshot.transform.regex(