Check for connection state before sending flush character

app/assets/javascripts/editor/websocket.js

@@ -4,8 +4,10 @@ CommandSocket = function(url, onOpen) {
   this.websocket.onopen = onOpen;
   this.websocket.onmessage = this.onMessage.bind(this);
   this.websocket.flush = function () {
+    if (this.readyState === this.OPEN) {
         this.send('\n');
     }
+  }
 };
 
 CommandSocket.prototype.onError = function(callback){