Hold outbound queue until device ready.

src/lib/device.ts

@@ -343,6 +343,10 @@ export default abstract class Device extends js.global.EventEmitter {
 
 	// Hot eats, cool treats
 	private dequeue(): void {
+		if (!this.ready) {
+			this.on('ready', this.dequeue.bind(this));
+			return;
+		}
 		const buf = this.queue.shift();
 		if (buf === undefined) return;
 		this.sendToDevice(buf);