It does not work:
That links let's you open the google hangouts application, however it does not work when you want to invite people. Check that after opening the application, the link to invite other people is set to https://plus.google.com/hangouts/_/meet/. If you send the link to somebody else it will try to create a new hangout (that will have the exact same issue).
Just go to https://plus.google.com/hangouts/_ -- It'll generate a new one and take you to it. I have this bookmarked on my address book too so it's just one click to make a new hangout.
Thanks!
This link works fine. I was not aware of it existence. I has a too long URI but it is way better than having to go to google plus and go to the the bottom right corner so that start a hangout button appears.
I am going to replace my Start button created by hangouts js library with a link to this URI.
EDIT: I just replaced the google hangout button created via js with google's framework by a direct link :).