Fix unhandled null for Task IO fields
required_input_names
, optional_input_names
and output_names
can be null
: https://ewoksserver.readthedocs.io/en/latest/restapi.html#tag/tasks/operation/get_task_api_task__identifier__get
required_input_names
, optional_input_names
and output_names
can be null
: https://ewoksserver.readthedocs.io/en/latest/restapi.html#tag/tasks/operation/get_task_api_task__identifier__get