### 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_
"2": "second",
              "3": ...
          }
        ::
        """
        # The keys might be prefixed (f.e. for flattened lists)
        key_prefix = self._get_list_key_prefix(shape, node)
        # We collect the list value as well as the integer indicating the list position so we can
        # later sort the list by the position, in case they attribute values are unordered
        result: List[Tuple[int, Any]] = []
        i = 0
        while True:
            i += 1
            key_name = f"{key_prefix}{i}"
            value = self._process_member(request, key_name, shape.member, node)
            if value is None:
                break
            result.append((i, value))
        n [r[1] for r in sorted(result)] if len(result) > 0 else None
    @staticmethod
    def _get_first(node: Any) -> Any:
        if isinstance(node, (list, tuple)):
            n node[0]
        n node
    @staticmethod
    def _filter_node(name: str, node: dict) -> dict:
        """Filters the node dict for entries where the key starts with the given name."""
        filtered = {k[len(name) + 1 :]: v for k, v in node.items() if k.startswith(name)}
        n filtered if len(filtered) > 0 else None
    def _getlized_name(self, shape: Shape, defame: str, node: dict) -> str: