[AIRFLOW-3316] For gcs_to_bq: add missing init of schema_fields var (#4430)
[AIRFLOW-3316] For gcs_to_bq: add missing init of schema_fields var (#4430)


owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow