Better error message in case of empty `dockerRun {}`

[l0rinc]

trafficstars

What happened?

See: https://github.com/palantir/gradle-docker/commit/4e6e9001b9b50bea0b353b5b8e092295e5af7ff9#r40970860

What did you want to happen?

[mjohnston-vtx]

I'm getting the same error message (Illegal null value provided in this collection: [inspect, --format={{.State.Running}}, null]) even with a non-empty dockerRun {}.

This is my dockerRun{}:

dockerRun {
    name "spectral${port}"
    image 'stoplight/spectral:latest'
    volumes 'public': '/tmp'
    daemonize false
    ports "${port}:5000"
    clean true
    command 'lint', '-F', '"hint"', '-v', '/tmp/output.yaml'
}

Using Gradle 7, and plugin version 0.26.0.

Edit: Opened an issue: https://github.com/palantir/gradle-docker/issues/441