Interfacing with the MongoDB server with only system DBs defined causes an error

[anbrenna]

It seems there is a problem with agent execution when the MongoDB server contained only system DBs.
Following the error:
Dec 22 09:04:37 ercole-agent[17820]: Invalid hostdata:
Dec 22 09:04:37 ercole-agent[17820]: - features.mongodb: Must validate at least one schema (anyOf). Value: [map[instances:[map[dbStats: dbs:0 name:erclmongo1.public.erco>
Dec 22 09:04:37 ercole-agent[17820]: - features.mongodb.instances.0.dbStats: Invalid type. Expected: array, given: null. Value: []
Dec 22 09:04:37 ercole-agent[17820]: [23-12-22 09:04:37][AGEN][WARN][/root/project/cmd/serve.go:205] Sending result: FAILED