Error in autodiscover provider settings - unexpected type <nil>

Hi,

I'm deploying my filebeat to collect log in a specific namespace. My chart looks like the following:

autodiscover:
enabled: true
namespace: ".RELEASE.NAMESPACE"
logplane: kubelog
json:
enabled: true
target: "json"
hints:
enabled: false
inclusions:
# - field: "kubernetes.annotations.collect"
# value: "true"
exclusions:
# - field: "kubernetes.annotations.drop"
# value: "true"

After installation I see my filebeat running (container created correctly) , but no logs is sent out to logstash. The logs reports the following periodic error:
ERROR
instance/beat.go:911
Exiting: error in autodiscover settings: unexpected type of

Can anyone help?

Regards,
Antonio