mocha.run() never return error status on browser

[nopnop]

Mocha.prototype.run([callback]) provide an error status to the callback (0/1).
But this value is not forwarded to the browser callback.

Example:

mocha.run(function(err) {
  console.log(err); // Always undefined
})

[nopnop]

Thanks.
Maybe you forgot to re-compile the browser version in the last release (1.19.0) so the issue remain unfixed.
(I could have provide a compiled version of browser.js in my PR, but I thought it was not a good practice: Was I wrong ?)