### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

There is an issue with `get-object-attributes` command which results in below error always: 
`aws --endpoint-url=http://localhost:4566 s3api get-object-attributes --bucket s3mock --key 20.txt --object-attributes "ObjectSize"`
````

> Response:  Unable to parse response (syntax error: line 1, column 0), invalid XML received. Further retries may succeed:
b'98\n5\n'
````

### How are you starting LocalStack?

With a docker-compose file

### Steps To Reproduce

#### Using docker-compse.yaml to start localstack

docker-compse.yaml:

```
localstack:
    image: localstack/localstack:latest
    ports:
      - '4563-4599:4563-4599'
      - '8055:8080'
    environment:
      - SERVICES=s3
      - DEBUG=1
      - LS_LOG=error
      - DATA_DIR=/tmp/localstack/data
      - AWS_DEFAULT_REGION=eu-west-1
      # - EDGE_PORT=4566
    volumes:
      - "./.localstack:/tmp/localstack"
      - "/var/run/docker.sock:/var/run/docker.sock"
```

#### cli commands to reproduce the issue

1. Create a Bucket: `aws --endpoint-url=http://localhost:4566 s3 mb s3://s3mock`
2. Create an Object: `aws --endpoint-url=http://localhost:4566 s3 cp data/20.txt s3://s3mock`

File 20.txt content are 2-digit numbers separated by newline.

3. get-object-attributes for object 20.txt :
```

 aws --endpoint-url=http://localhost:4566 s3api get-object-attributes --bucket s3mock --key 20.txt --object-attributes "ObjectSize"

```
Results in error:

> Unable to parse response (syntax error: line 1, column 0), invalid XML received. Further retries may succeed:
b'98\n5\n'



### Environment

```markdown
- OS:Mac 12.x
- LocalStack:latest
- Node 14
```


### Anything else?

_No response_
"""
    The ``QueryRequesr`` is responsible for parsing incoming requests for services which use the ``query``
    protocol. The requests for these services encode the majority of their parameters in the URL query string.
    **Experimental:** This parser is still experimental.
    When implementing services with this parser, some edge cases might not work out-of-the-box.
    """
    @_handle_exceptions
    def parse(self, request: HttpRequestuple[OperationModel, Any]:
        instance = request.values
        if "Action" not in instance:
            raise ProtocolParserError(
                f"Operation detection failed. "
                f"Missing Action in request for query-protocol service {self.service}."
            )
        action = instance["Action"]
        try:
            operation: OperationModel = self.service.operation_model(action)
        except OperationNotFoundError as e:
            raise OperationNotFoundParserError(
                f"Operation detection failed."
                f"Operation {action} could not be found for service {self.service}."
            ) from e
        # There are no uri params in the query protocol (all ops are POST on "/")
        uri_params = {}
        input_shape: StructureShape = operation.input_shape
        parsed = self._parse_shape(request, input_shape, instance, uri_params)
        if parsed is None:
            n operation, {}
        n operation, parsed
    def _process_member(