Javascript executeCommandLine fails when no timeout

according to the Javascript documentation the time argument is optional but when I DONT code the command fails.

Exec.executeCommandLine(String... commandLine)
Exec.executeCommandLine(Duration timeout, String... commandLine)
var Exec = Java.type("org.openhab.core.model.script.actions.Exec");
var Duration = Java.type("java.time.Duration");
//var response = Exec.executeCommandLine("/opt/");  // fails
var response = Exec.executeCommandLine(Duration.ofSeconds(5),"/opt/"); //works!!"gotResult:" + response);

What the error?

Note it’s only optional if you don’t care what the response from the command is. Without the Duration that call to executeCommandLine immediately exits and response will be null.