Hello all,
I'm trying to dynamically create parallel jobs. My code works as expected but the job still fails with:

hudson.remoting.ProxyException: org.codehaus.groovy.runtime.typehandling.GroovyCastException: Cannot cast object '{test-qucli=null, test-composer=null}' with class 'java.util.HashMap' to class 'org.jenkinsci.plugins.pipeline.modeldefinition.model.Root' due to: groovy.lang.GroovyRuntimeException: Could not find matching constructor for: org.jenkinsci.plugins.pipeline.modeldefinition.model.Root(java.util.HashMap) 

The error does not appear when I comment out the last block ("Clean") in the runPipeline method.
I'm quite certain that this isn't a bug. But I hit a wall and neither IRC nor mailing list responded. So, sorry about that. Also I'm not familiar with Groovy and the code looks accordingly.

If I am at the wrong place, could you please point me somewhere where I might find help?

Jenkinsfile and the complete error is attached.