message: throw exception with undefined containerRunner and docker
diff: @@ -143,7 +143,12 @@ export class TechdocsGenerator implements GeneratorBase {
  );
  break;
  case 'docker':
  - await this.containerRunner!.runContainer({
  + if (this.containerRunner === undefined) {
  + throw new Error(
  + "Invalid state: containerRunner cannot be undefined when runIn is 'docker'",
  + );
  + }
  + await this.containerRunner.runContainer({
  imageName:
  this.options.dockerImage ?? TechdocsGenerator.defaultDockerImage,
  args: ['build', '-d', '/output'],
  