Finds a crashed thread by iterating all threads and checking
whether they've crashed. If they have we short circuit and
return the thread. Otherwise we return the crashed_thread entry.

@param report the JSON report structure.
@returns {*} the entry of the crashed thread.
function get_crash_thread(report) {
  var crash   = report['crash'] || {};
  var threads = crash['threads'] || [];

  var thread = threads.find(function (thread) {
    return !!thread['crashed'];
  });

  return thread || crash['crashed_thread'];
}