Unable to export default namespace only with querystring

[wfjsw]

As previously discussed in Slack.

*   Trying 127.0.0.1:21062...
* Connected to 127.0.0.1 (127.0.0.1) port 21062 (#0)
> GET /v2/projects/1/export?languages=zh-Hans&format=JSON&zip=false&structureDelimiter=&filterNamespace= HTTP/1.1
> Host: 127.0.0.1:21062
> User-Agent: curl/7.74.0
> Accept: */*
> X-Api-Key: scrubbed
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 400 
< Vary: origin,access-control-request-method,access-control-request-headers,accept-encoding
< X-Content-Type-Options: nosniff
< X-XSS-Protection: 1; mode=block
< Cache-Control: no-cache, no-store, max-age=0, must-revalidate
< Pragma: no-cache
< Expires: 0
< X-Frame-Options: SAMEORIGIN
< Content-Type: application/json
< Transfer-Encoding: chunked
< Date: Wed, 26 Apr 2023 13:41:52 GMT
< Connection: close
< 
* Closing connection 0
{"code":"multiple_files_must_be_zipped","params":null}

*   Trying 127.0.0.1:21062...
* Connected to 127.0.0.1 (127.0.0.1) port 21062 (#0)
> GET /v2/projects/1/export?languages=zh-Hans&format=JSON&zip=false&structureDelimiter=&filterNamespace=a HTTP/1.1
> Host: 127.0.0.1:21062
> User-Agent: curl/7.74.0
> Accept: */*
> X-Api-Key: scrubbed
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 400 
< Vary: origin,access-control-request-method,access-control-request-headers,accept-encoding
< X-Content-Type-Options: nosniff
< X-XSS-Protection: 1; mode=block
< Cache-Control: no-cache, no-store, max-age=0, must-revalidate
< Pragma: no-cache
< Expires: 0
< X-Frame-Options: SAMEORIGIN
< Content-Type: application/json
< Transfer-Encoding: chunked
< Date: Wed, 26 Apr 2023 13:41:52 GMT
< Connection: close
< 
* Closing connection 0
{
    "foo": "bar"
}