message: KeyRequestHandler: clear redundant users/devices on cancellations
  ... otherwise _processNextRequest will get confused
diff: @@ -88,6 +88,12 @@ export default class KeyRequestHandler {
  }
  console.log("Forgetting room key request");
  requests.splice(idx, 1);
  + if (requests.length === 0) {
  + delete this._pendingKeyRequests[userId][deviceId];
  + if (Object.keys(this._pendingKeyRequests[userId]).length === 0) {
  + delete this._pendingKeyRequests[userId];
  + }
  + }
  }
  _processNextRequest() {
  