seCustomSlaveDelivery.js doesn't fullfill order for mutes

When placing a custom order for a mute individual, this code(in generateDelivery() of App.Events.SEcustomSlaveDelivery):

if (V.customSlave.voice && V.customSlave.voice !== -1) {
      delivery.voice = V.customSlave.voice;
} else {
      delivery.voice = random(0, 3);
}

prevents that order to be honored(it might randomly get a mute though).

This happens because a value of 0 is considered as 'false' by js, so both checks in the if evaluate to false.