Loading a work crashes when oa_status is blank

[v0idness]

Hi,

I'm experiencing the following issue whenever I retrieve a work that has no information given for the oa_status variable (example: https://api.openalex.org/works/W2150191218):

oa = openalexapi.OpenAlex()
oa.get_single_work("https://openalex.org/W2150191218")

yields:

Traceback (most recent call last):
File "mappings/openalex.py", line 5, in
oa.get_single_work("https://openalex.org/W2150191218")
File "env/lib/python3.8/site-packages/openalexapi/init.py", line 35, in get_single_work
return Work(**response.json())
File "pydantic/main.py", line 341, in pydantic.main.BaseModel.init
pydantic.error_wrappers.ValidationError: 1 validation error for Work
open_access -> oa_status
none is not an allowed value (type=type_error.none.not_allowed)