VR keyboard extra keys: the helper reconnects when Steam's page closes while connecting

A CDP call sent after the socket closed (e.g. Steam restarting between
Runtime.enable and the first inject) waited forever, so the helper hung
instead of reconnecting. Such calls now resolve empty at once.

modules/vr-keyboard-extra-keys/xdotool-helper.mjs

@@ -52,6 +52,7 @@ async function session() {
   let id = 0;
   const pending = new Map();
   const call = (method, params = {}) => new Promise((res) => {
+    if (ws.readyState !== WebSocket.OPEN) return res({});   // closed: never answered
     const i = ++id; pending.set(i, res); ws.send(JSON.stringify({ id: i, method, params }));
   });
   let last;                                       // logged when it changes (e.g. a signature error once, not every 15 s)