Bug Report

What did you do?
A clear and concise description of the steps you took (or insert a code snippet).

gen-csv works with operator-sdk 0.8.0 but not 0.11.0. Reproduce by cloning github.com/openshift-knative/knative-kafka-operator at commit c97a6cd and following these steps:

[aconway@grommit knative-kafka-operator (master=)]$ ~/Downloads/operator-sdk-v0.8.0-x86_64-linux-gnu  olm-catalog gen-csv --update-crds --csv-version 0.9.0 --from-version 0.8.2
INFO[0000] Generating CSV manifest version 0.9.0        
INFO[0000] Created deploy/olm-catalog/knative-kafka-operator/0.9.0/knative-kafka-operator.v0.9.0.clusterserviceversion.yaml 
[aconway@grommit knative-kafka-operator (master=)]$ ~/Downloads/operator-sdk-v0.11.0-x86_64-linux-gnu  olm-catalog gen-csv --update-crds --csv-version 0.9.0 --from-version 0.8.2
INFO[0000] Generating CSV manifest version 0.9.0        
INFO[0000] Created deploy/olm-catalog/knative-kafka-operator/0.9.0/knative-kafka-operator.v0.9.0.clusterserviceversion.yaml 
Error: catalog scaffold failed: (failed to validate package manifest knative-kafka-operator: default channel cannot be empty)

What did you expect to see?
Both work.

What did you see instead? Under which circumstances?
0.8.0 worked, 0.11.0 failed.

Environment

• operator-sdk version:
  0.8.0 and 0.11.0

• go version:
  go version go1.12.10 linux/amd64

• Kubernetes version information:
  NA

• Kubernetes cluster kind:
  NA

• Are you writing your operator in ansible, helm, or go?
  Go

Possible Solution
I'm not sure if this is a regression in operator-sdk, or if there is some problem in our YAML files that is being detected by the newer version and not the older one.

Additional context
Add any other context about the problem here.