Error when launching Bull many times

Created by: lchenay

This happen when using cluster or when launching Bull in different server.

TypeError: Cannot call method 'takeLock' of null
  File "/app/node_modules/bull/lib/queue.js", line 357, in Queue.processStalledJob
      return job.takeLock(_this.token).then(function(lock){
  File "/app/node_modules/bull/node_modules/when/sequence.js", line 34, in <unknown>
                    return when(task.apply(null, args), addResult);
  File "/app/node_modules/bull/node_modules/when/when.js", line 652, in <unknown>
                            return reduceFunc(c, value, i, total);
  File "/app/node_modules/bull/node_modules/when/when.js", line 355, in Object.then
                        ? coerce(onFulfilled(value)) : self;
  File "/app/node_modules/bull/node_modules/when/when.js", line 258, in <unknown>
                        value.then(onFulfilled, onRejected, onProgress)
  File "/app/node_modules/bull/node_modules/when/when.js", line 735, in Object.drainQueue [as _onImmediate]
                task();
  File "timers.js", line 345, in processImmediate [as _immediateCallback]