If you do not give any context, it is too difficult to help you. Throw here an exception is a bad practice in a community.
Looking at your exception, the error is in line 44 of your pipeline script:
at WorkflowScript.run(WorkflowScript:44)
And it seems like you accessing a property that does not exist in the object you are accessing
groovy.lang.MissingPropertyException: No such property: robocopyExitCode for class: groovy.lang.Binding