https://www.mavensecurity.com/blog/getting-started-with-frida-on-android - Fix

android-load-classes.js

"use strict";


/* Check if a Java/Dalvik/ART VM is available */
if (Java.available) {

  //FIX - Need to be inside perform 
  Java.perform(function() {
    
    /* enumerate loaded classes */
    Java.enumerateLoadedClasses({
        /* when a class is found send it to the client */
        onMatch: function(className) {
            send(className);
        },
        /* when we are done enumerating classes send "done" to the client */
        onComplete: function() {
            send("done");
        }
    });
    });
/* if a Java/Dalvik/ART VM is not available */
} else {
    send("Java not available in this process");
}