java.lang.NullPointerException: Cannot get property (property) on null object

#!/usr/bin/env groovy

def call(body) {
    def config = [:]
    body.resolveStrategy = Closure.DELEGATE_FIRST
    body.delegate = config
    body()

    node {
        echo "config=${config}"
    }
}

#!groovy

@Library('shared-test') _

properties( [
    parameters([
        booleanParam(name:'truefalse', defaultValue:true, description:'boolean')
        ,string(name:'stringthing', defaultValue:'mary had a little lamb', description:'string')
    ])
] )

paramEcho {
    booleanvalue = params.truefalse
    stringvalue = params.stringthing
}

[Pipeline] properties
[Pipeline] End of Pipeline
java.lang.NullPointerException: Cannot get property 'truefalse' on null object
 at org.codehaus.groovy.runtime.NullObject.getProperty(NullObject.java:60)
 at org.codehaus.groovy.runtime.InvokerHelper.getProperty(InvokerHelper.java:174)
 at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.getProperty(ScriptBytecodeAdapter.java:456)
 at org.kohsuke.groovy.sandbox.impl.Checker$6.call(Checker.java:290)
 at org.kohsuke.groovy.sandbox.impl.Checker.checkedGetProperty(Checker.java:292)
 at com.cloudbees.groovy.cps.sandbox.SandboxInvoker.getProperty(SandboxInvoker.java:29)
 at com.cloudbees.groovy.cps.impl.PropertyAccessBlock.rawGet(PropertyAccessBlock.java:20)
 at WorkflowScript.run(WorkflowScript:14)
 at paramEcho.call(/var/lib/jenkins/jobs/test-jobs/jobs/test-paramEcho/builds/1/libs/shared-test/vars/paramEcho.groovy:7)
 at WorkflowScript.run(WorkflowScript:13)
 at ___cps.transform___(Native Method)
 at com.cloudbees.groovy.cps.impl.PropertyishBlock$ContinuationImpl.get(PropertyishBlock.java:74)
 at com.cloudbees.groovy.cps.LValueBlock$GetAdapter.receive(LValueBlock.java:30)
 at com.cloudbees.groovy.cps.impl.PropertyishBlock$ContinuationImpl.fixName(PropertyishBlock.java:66)
 at sun.reflect.GeneratedMethodAccessor341.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
 at java.lang.reflect.Method.invoke(Method.java:498)
 at com.cloudbees.groovy.cps.impl.ContinuationPtr$ContinuationImpl.receive(ContinuationPtr.java:72)
 at com.cloudbees.groovy.cps.impl.ConstantBlock.eval(ConstantBlock.java:21)
 at com.cloudbees.groovy.cps.Next.step(Next.java:83)
 at com.cloudbees.groovy.cps.Continuable$1.call(Continuable.java:174)
 at com.cloudbees.groovy.cps.Continuable$1.call(Continuable.java:163)
 at org.codehaus.groovy.runtime.GroovyCategorySupport$ThreadCategoryInfo.use(GroovyCategorySupport.java:122)
 at org.codehaus.groovy.runtime.GroovyCategorySupport.use(GroovyCategorySupport.java:261)
 at com.cloudbees.groovy.cps.Continuable.run0(Continuable.java:163)
 at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.access$101(SandboxContinuable.java:34)
 at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.lambda$run0$0(SandboxContinuable.java:59)
 at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.GroovySandbox.runInSandbox(GroovySandbox.java:108)
 at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.run0(SandboxContinuable.java:58)
 at org.jenkinsci.plugins.workflow.cps.CpsThread.runNextChunk(CpsThread.java:174)
 at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.run(CpsThreadGroup.java:332)
 at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.access$200(CpsThreadGroup.java:83)
 at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:244)
 at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:232)
 at org.jenkinsci.plugins.workflow.cps.CpsVmExecutorService$2.call(CpsVmExecutorService.java:64)
 at java.util.concurrent.FutureTask.run(FutureTask.java:266)
 at hudson.remoting.SingleLaneExecutorService$1.run(SingleLaneExecutorService.java:131)
 at jenkins.util.ContextResettingExecutorService$1.run(ContextResettingExecutorService.java:28)
 at jenkins.security.ImpersonatingExecutorService$1.run(ImpersonatingExecutorService.java:59)
 at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
 at java.util.concurrent.FutureTask.run(FutureTask.java:266)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
 at java.lang.Thread.run(Thread.java:748)
Finished: FAILURE

#!groovy

@Library('shared-test') _
properties( [
    parameters([
        booleanParam(name:'truefalse', defaultValue:true, description:'boolean')
        ,string(name:'stringthing', defaultValue:'mary had a little lamb', description:'string')
    ])
] )

def _booleanvalue = params.truefalse
def _stringvalue = params.stringthing

paramEcho {
    booleanvalue = _booleanvalue
    stringvalue = _stringvalue
}

[Pipeline] properties
[Pipeline] node
Running on Jenkins in /var/lib/jenkins/workspace/test-jobs/test-paramEcho
[Pipeline] {
[Pipeline] echo
config=[booleanvalue:true, stringvalue:mary had a little lamb]
[Pipeline] }
[Pipeline] // node
[Pipeline] End of Pipeline
Finished: SUCCESS 

config=[:]