A few debug tricks learned the hard way.
You require a module that when inspecting its value end to be an empty object. You check if the required path is valid (it should have thrown an error if so but any way). But after 1-2 hours, I ended typing exactly my problem "Required module empty" and looked at this stackoverflow.
It is a circular dependency problem, the required module have required in any way the module that try to require it... So double check your modules architecture.
Here a simple and eficient way for ubuntu servers https://askubuntu.com/questions/426750/how-can-i-update-my-nodejs-to-the-latest-version