[socket] fixed a "xhr undefined" bug

vispa/static/js/common/socket.js

@@ -277,8 +277,8 @@ define(["jquery", "emitter"], function($, Emitter) {
       });
 
       timeout = setTimeout(function() {
-        if (xhr.state() == "pending") {
-          xhr.abort("connection timeout (" + self.options.pollGracePeriod + ")");
+        if (self.xhr.state() == "pending") {
+          self.xhr.abort("connection timeout (" + self.options.pollGracePeriod + ")");
         }
       }, this.options.pollGracePeriod);
 
@@ -314,12 +314,12 @@ define(["jquery", "emitter"], function($, Emitter) {
     }
   });
 
-  
+
   Socket.PollSocket = PollSocket;
 
   // define common states
   Socket.states = {
-    CONNECTING: 0, 
+    CONNECTING: 0,
     CONNECTED : 1,
     CLOSING   : 2,
     CLOSED    : 3