### 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_
topic_name = "queue-{}".format(short_uid())
        queue_name = "test-%s" % short_uid()
        topic_arn = self.sns_client.create_topic(Name=topic_name)["TopicArn"]
        queue = self.sqs_client.create_queue(QueueName=queue_name)
        queue_url = queue["QueueUrl"]
        queue_arn = aws_stack.sqs_queue_arn(queue_name)
        subscription = self.sns_client.subscribe(
            TopicArn=topic_arn, Protocol="sqs", Endpoint=queue_arn
        )
        subscription_attributes = self.sns_client.get_subscription_attributes(
            SubscriptionArn=subscription["SubscriptionArn"]
        )
        self.assertEqual(
            subscription_attributes.get("Attributes").get("SubscriptionArn"),
            subscription["SubscriptionArn"],
        )
        self.sns_client.unsubscribe(SubscriptionArn=subscription["SubscriptionArn"])
        with self.assertRaises(ClientError) as ctx:
            self.sns_client.get_subscription_attributes(
                SubscriptionArn=subscription["SubscriptionArn"]
            )
        self.assertEqual(ctx.exception.response["Error"]["Code"], "NotFound")
        self.assertEqual(ctx.exception.response["ResponseMetadata"]["HTTPStatusCode"], 404)
        # c
        self.sns_client.delete_topic(TopicArn=topic_arn)
        self.sqs_client.delete_queue(QueueUrl=queue_url)