### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

When you publish a message to SNS without a *body* (e.g. only attributes) it succeeds.

### Expected Behavior

Trying to publish a message without a *body* should fail (at least it does when trying to do this in AWS)

### How are you starting LocalStack?

Custom (please describe below)

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

using Java testcontainers...

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

```bash
#!/bin/sh
 
queue_arn=$(awslocal sqs create-queue --queue-name $QUEUE_NAME --output text)
echo "Queue ARN: $queue_arn"

topic_arn=$(awslocal sns create-topic --name $TOPIC_NAME --output text)
echo "Topic ARN: $topic_arn"

subscription_arn=$(awslocal sns subscribe \
    --attributes RawMessageDelivery=true \
    --topic-arn "$topic_arn" \
    --protocol sqs \
    --notification-endpoint "$queue_arn" \
    --output text)
echo "Subscription ARN: $subscription_arn" 
```


### Environment

```markdown
- OS: OSX 11.5.2
- LocalStack: 0.13.0
- Docker Desktop: v20.10.8
```


### Anything else?

_No response_
cls.sqs_client = aws_stack.connect_to_service("sqs")
        cls.sns_client = aws_stack.connect_to_service("sns")
        cls.topic_arn = cls.sns_client.create_topic(Name=TEST_TOPIC_NAME)["TopicArn"]
        cls.queue_url = cls.sqs_client.create_queue(QueueName=TEST_QUEUE_NAME)["QueueUrl"]
        cls.dlq_url = cls.sqs_client.create_queue(QueueName=TEST_QUEUE_DLQ_NAME)["QueueUrl"]
    @classmethod
    def tearDownClass(cls):
        cls.sqs_client.delete_queue(QueueUrl=cls.queue_url)
        cls.sqs_client.delete_queue(QueueUrl=cls.dlq_url)
        cls.sns_client.delete_topic(TopicArn=cls.topic_arn)
    def test_publish_unicode_chars(self):
        
        _, queue_arn, queue_url = self._create_queue()
        self.sns_client.subscribe(TopicArn=self.topic_arn, Protocol="sqs", Endpoint=queue_arn)
        
        message = 'ö§a1"_!?,. £$-'
        self.sns_client.publish(TopicArn=self.topic_arn, Message=message)
        def check_message():
            msgs = self.sqs_client.receive_message(QueueUrl=queue_url)
            msg_received = msgs["Messages"][0]
            msg_received = json.loads(to_str(msg_received["Body"]))
            msg_received = msg_received["Message"]
            self.assertEqual(message, msg_received)
        retry(check_message, retries=PUBLICATION_RETRIES, sleep=PUBLICATION_TIMEOUT)
        # c
        self.sqs_client.delete_queue(QueueUrl=queue_url)
    def test_subscribe_http_endpoint(self):
        # c
        class MyUpdateListener(ProxyListener):