xP: only care about RPC results if requested

This prevents "No response" errors from firing for most commands.

xP/public/xP.js

@@ -4,7 +4,7 @@ import * as Relay from './proto.js'
 
 // ---- RPC --------------------------------------------------------------------
 
-class RelayRpc extends EventTarget {
+class RelayRPC extends EventTarget {
 	constructor(url) {
 		super()
 		this.url = url
@@ -72,7 +72,7 @@ class RelayRpc extends EventTarget {
 			if (this.promised[e.commandSeq] !== undefined)
 				this.promised[e.commandSeq].reject(e.error)
 			else
-				console.error("Unawaited error")
+				console.error(`Unawaited error: ${e.error}`)
 			break
 		case Relay.Event.Response:
 			if (this.promised[e.commandSeq] !== undefined)
@@ -109,9 +109,16 @@ class RelayRpc extends EventTarget {
 			seq = this.commandSeq = 0
 
 		this.ws.send(JSON.stringify({commandSeq: seq, data: params}))
-		return new Promise((resolve, reject) => {
-			this.promised[seq] = {resolve, reject}
-		})
+
+		// Automagically detect if we want a result.
+		let data = undefined
+		const promise = new Promise(
+			(resolve, reject) => { data = {resolve, reject} })
+		promise.then = (...args) => {
+			this.promised[seq] = data
+			return Promise.prototype.then.call(promise, ...args)
+		}
+		return promise
 	}
 }
 
@@ -173,7 +180,7 @@ function updateIcon(highlighted) {
 
 // ---- Event processing -------------------------------------------------------
 
-let rpc = new RelayRpc(proxy)
+let rpc = new RelayRPC(proxy)
 let rpcEventHandlers = new Map()
 
 let buffers = new Map()