When running next pipeline script https://gist.github.com/lordofthejars/be8c2384db1ce5207f0336e690e3367c and after its execution, you get next screen https://postimg.org/image/yvaeo4hc5/ instead of something like https://jenkins.io/images/post-images/blueocean/pipeline-run.png

I am running Jenkins 2.20 and blue ocean 1.0.0-b01.