oc-mirror produces catalog artifacts with empty channels when imageset config filters operator to specific version

[bkkhoo]

Version

$ oc-mirror version
v0.1.0-alpha.3

What happened?

Executing oc-mirror --config imageset-config.yaml file://output-dir with the following config to mirror to directory:

apiVersion: tmp-redhatgov.com/v1alpha1
kind: ImageSetConfiguration
mirror:
  operators:
    - catalog: registry.redhat.io/redhat/redhat-operator-index:v4.9
      headsOnly: false
      packages:
        - name: rhacs-operator
          channels:
          - name: latest
          versions:
          - '3.67.0'

The command completed successfully, but some of the channels have empty entris:

{
    "schema": "olm.channel",
    "name": "rhacs-3.66",
    "package": "rhacs-operator",
    "entries": []
}

opm validate of the catalog show this:

$ opm validate output-dir/oc-mirror-workspace/src/catalogs
FATA[0000] invalid index:
└── invalid package "rhacs-operator":
    ├── invalid channel "rhacs-3.62":
    │   └── channel must contain at least one bundle
    ├── invalid channel "rhacs-3.64":
    │   └── channel must contain at least one bundle
    ├── invalid channel "rhacs-3.65":
    │   └── channel must contain at least one bundle
    └── invalid channel "rhacs-3.66":
        └── channel must contain at least one bundle

What you expected to happen?

Empty channels should be removed, catalog image with empty channels will not run.

[jpower432]

Linking this PR in operator-registry. Will fix this issue. operator-framework/operator-registry#884