argo-events: get "trigger must define a name" error when following calendar readme

Describe the bug I am following https://github.com/argoproj/argo-events/blob/master/gateways/core/calendar/install.md

after install sensor

kubectl -n argo-events create -f https://github.com/argoproj/argo-events/blob/master/examples/sensors/calendar.yaml

didn’t see calendar-sensor pod created. Saw this logs in sensor-controller.

2019-03-18T19:47:04Z | error | msg: failed to validate sensor |  error="trigger must define a name" sensor-name:calendar-sensor sensor-namespace:argo-events

Environment:

• Minikube v0.34.1