### 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_
):
                parsed[member_name] = self._parse_shape(
                    request, member_shape, member_node, uri_params
                )
            elif member_shape.ization.get("xmlAttribute"):
                attributes = {}
                location_name = member_shape.ization["name"]
                for key, value in node.attrib.items():
                    new_key = self._namespace_re.sub(location_name.split(":")[0] + ":", key)
                    attributes[new_key] = value
                if location_name in attributes:
                    ocation_name]
            elif member_name in shape.required_members:
                # If the member is required, but not existing, we explicitly set None
                parsed[member_name] = None
        n parsed
    def _parse_map(
        self,
        request: HttpRequest,
        shape: MapShape,
        node: dict,
        
    ) -> dict:
        parsed = {}
        key_shape = shape.key
        value_shape = shape.value
        key_location_name = key_shape.ization.get("name", "key")
        value_location_name = value_shape.ization.get("name", "value")
        if shape.ization.get("flattened") and not isinstance(node, list):
            node = [node]