A NullPointerException with no stacktrace is experienced when trying to run the following pipeline:

pipeline {
    agent any
    stages {
        stage('stage usernameColonPassword') {
            steps {
                sh 'echo usernameColonPassword 1'
                withCredentials([usernameColonPassword(credentialsId: 'mysecret', variable: 'SECRET')]) {
                    sh 'echo usernameColonPassword 2' 
                }
            }
        }
        stage('stage usernamePassword') {
            steps {
                sh 'echo usernamePassword 3'
                withCredentials([usernamePassword(credentialsId: 'mysecret', passwordVariable: 'SECRET2')]) {
                    sh 'echo usernamePassword 4' 
                }
            }
        }
    }
}

where "mysecret" is a credential with it's "kind" being "username and password".

This exception causes the job to fail.

Specifically, `usernameColonPassword` succeeds, while `usernamePassword` fails; `usernamePassword 4` is never printed to the log.

This was the first time I have tried to run this script, so I have never observed this succeeding; for all I know, it has always failed.

My workaround options are bad:  either parse the password out of the `user:pass` format, or abandon the plugin.

UPDATE: as mentioned in the comments, there is a better workaround.  This ticket is now for removing or documenting the requirement for all arguments to be used, and creating a useful error message.