Fix `badarg` when querying replicator's _scheduler/docs endpoint
Fix `badarg` when querying replicator's _scheduler/docs endpoint

Jira: COUCHDB-3324

fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb