Failing to load drifter_fieldset

[ammedd]

virtualship run PATH
tries to load drifter_fieldset even when no drifters are specified in schedule.yaml

Error message:
File "/Users/0448257/virtualship/src/virtualship/cli/commands.py", line 179, in run
do_expedition(Path(path))
File "/Users/0448257/virtualship/src/virtualship/expedition/do_expedition.py", line 54, in do_expedition
input_data = _load_input_data(
File "/Users/0448257/virtualship/src/virtualship/expedition/do_expedition.py", line 145, in _load_input_data
return InputData.load(
File "/Users/0448257/virtualship/src/virtualship/expedition/input_data.py", line 47, in load
drifter_fieldset = cls._load_drifter_fieldset(directory)
File "/Users/0448257/virtualship/src/virtualship/expedition/input_data.py", line 128, in _load_drifter_fieldset
"U": directory.joinpath("drifter_uv.nc"),
AttributeError: 'NoneType' object has no attribute 'joinpath'