So, I digged deeper into this error and also found an issue over at the GitHub project which is describing what I thought was exactly my problem too.
It turns out that somehow Ember App Kit (or even Ember itself) is swallowing messages/errors thrown by Ember.assert
and the like so that I followed the suggestion of Stefan Penner and switched to pause on caught exceptions within my browsers dev tools and I saw that it's not one, but several errors!
Unfortunately all these errors fail silently until the last error cannot be caught anymore which is why every error showed the same Stack Trace...
So, the solution seems to be to be sure to pause on caught exceptions
and trace down the error message in Ember.assert()
... has anybody else seen the same problem and has some other suggestions or could approve my conclusion?
Screenshot of "pause on caught exceptions" in Chrome Dev Tools: