Undefined requestsPerSeconds gives an infinite loop

[amrltqt]

Several days ago, I've made a typo while configuring a PromiseThrottle on the requestsPerSeconds awaited field. Consequently, the object was configured with an undefined requestsPerSeconds value and my sequence of promise was obviously not fired.

After a small deep diving a bit, I've finally understood that the undefined have been transformed into a NaN while computing the value inc = (1000 / this.requestsPerSecond) * weight. The NaN is propagated in the instruction on below and make the if (the this._execute();) unsolvable.

if (elapsed >= inc) {
    this._execute();
} else {
    // we have reached the limit, schedule a dequeue operation
    setTimeout(function() {
        this.dequeue();
    }.bind(this), inc - elapsed);
}

Is it possible to add some warning or trigger some error in case of undefined or NaN value? I would be happy to send you a PR for that if you need to!