cjio returns broken glb when converting an "empty" cityjson

[pcace]

trying to convert an empty cityJson file to glb results in a not correct (completely empty) glb file.
i'd expect the result still to be a valid glb file

this is an example cityjson:
{"type":"CityJSON","version": "1.1","transform": {"scale": [1.0, 1.0, 1.0],"translate": [0.0, 0.0, 0.0]},"CityObjects": {},"vertices": []}

this would be the used command: cjio tmp/emptyCity.json export glb tmp/broken.glb

if i miss something please let me know!

Thanks a lot!