Set empty array as default value in array_agg in postgresql

I have a view:

CREATE OR REPLACE VIEW microservice_view AS
  SELECT
    m.id :: BIGINT,
    m.name,
    m.sending_message_rate :: BIGINT,
    m.max_message_size :: BIGINT,
    m.prefetch_count :: BIGINT,
    (SELECT COALESCE(json_agg(DISTINCT node_id), '[]')
     FROM public.microservice_node
     WHERE microservice_id = m.id) AS nodes,

    (SELECT array_agg(DISTINCT json_build_object('id', transport_id :: INT,
                                                 'is_available', (credentials ->> 'is_available') :: BOOLEAN,
                                                 'username', credentials ->> 'username',
                                                 'password', credentials ->> 'password',
                                                 'default', (default_transport) :: BOOLEAN) :: JSONB
    )
     FROM transport_microservice
     WHERE microservice_id = m.id) AS transports
  FROM public.microservice m
  GROUP BY m.id
  ORDER BY m.id ASC;

Sometimes transports is null. How can I set an empty array as a default value for array_agg? This field should be an empty array or array with data. In some cases I use array_length function to filter the data.