I can't seem to send the error, but if you download the game you should receive the same thing, I'm gonna go to sleep now, so I'll check this all out in the morning.
I've made several tests. It seems your nw.js-version is not compatible with the plugin. I replaced the old plugin with the latest version, set up the correct parameters and updated the nw.js-version to 0.104.1 (the version I run my tests). Everything works fine.
If you want to check which nw.js-version you are using, type
nw.process.versions.nw
into the console.
If you want to update your nw.js-version, here is a step-by-step-guide to do so.
At the moment I don't know which version you need at least to run the latest version of the GameJolt-Plugin. But I recommend to update to the latest nw.js-version.
You may have to insert a name-property to your package.json. The property is there by default but empty. Just type any name in it.