### 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_
return make_error(
                        message="Token not specified in confirm subscription request",
                        code=400,
                    )
                do_confirm_subscription(req_data.get("TopicArn")[0], req_data.get("Token")[0])
            elif req_action == "Unsubscribe":
                if "SubscriptionArn" not in req_data:
                    return make_error(
                        message="SubscriptionArn not specified in unsubscribe request",
                        code=400,
                    )
                do_unsubscribe(req_data.get("SubscriptionArn")[0])
            elif req_action == "DeleteTopic":
                do_delete_topic(topic_arn)
            elif req_action == "Publish":
                if req_data.get("Subject") == [""]:
                    return make_error(code=400, code_string="InvalidParameter", message="Subject")
                sns_backend = SNSBackend.get()
                
                
                if "PhoneNumber" not in req_data and "TargetArn" not in req_data:
                    if topic_arn not in sns_backend.sns_subscriptions:
                        return make_error(
                            code=404,
                            code_string="NotFound",
                            message="Topic does not exist",
                        )
                message_id = publish_message(topic_arn, req_data, headers)
                
                return make_response(req_action, message_id=message_id)