In Jenkins, createItem triggers NotSerializableException, but does the job... should I be worried?

Question

I call createItem in a function, from a loop derived from the list of git's currentBuild.changeSets

Here is the function:

def boolean shCreateJob(jobName) {
    jobName = jobName.toString()
    command = "curl -s -XPOST '$JENKINS_URL/createItem?name=$jobName' -u user:secret --data-binary ${TEMPLATE_FILE} -H 'Content-Type:text/xml'"
    command = command.toString()
    println("In shCreateJob, command=$command")
    println("In shCreateJob, command.getClass()=${command.getClass()}")
    try {
        sh "curl $command"
        } 
    catch (err) {
            echo 'Exception during job creation : ' + err
        }
    return true
}

As you can see, in the function, I'm trying to cast the name and the command to String to ensure the sh command doesn't get anything exotic.

Here is the output:

In shCreateJob, command=curl -s -XPOST 'http://10.128.128.168:8080//createItem?name=cz_AAA' -u user:secret --data-binary @//var/lib/jenkins/jobs/_upload_template/config.xml -H 'Content-Type:text/xml'
[Pipeline] echo
In shCreateJob, command.getClass()=class java.lang.String
[Pipeline] sh
[Pipeline] echo
Exception during job creation : java.io.NotSerializableException: java.util.LinkedHashMap$Entry

And yet, the job ends in success, and also the new job is created as expected! What's the deal?