message: Stop sending help on client leave
diff: @@ -1069,7 +1069,9 @@ export class Document extends EventEmitter implements api.IDocument {
  this.clients.delete(leftClientId);
  this.emit("clientLeave", leftClientId);
  // Switch to read only mode if a client receives it's own leave message.
  + // Stop any pending help request.
  if (this.clientId === leftClientId) {
  + this.stopSendingHelp();
  this._deltaManager.enableReadonlyMode();
  } else {
  this.runTaskAnalyzer();
  