Prevent double userLeave

changelog

@@ -1,3 +1,7 @@
+Tue Nov 05 22:43 2013 CDT
+    * lib/channel.js: Set user.channel = null in userLeave to prevent
+      double execution of userLeave.
+
 Tue Nov 05 22:38 2013 CDT
     * lib/database.js: Add a check for registrations-in-progress to prevent
       duplicate queries by an impatient user

lib/channel.js

@@ -860,6 +860,7 @@ Channel.prototype.userJoin = function(user) {
 }
 
 Channel.prototype.userLeave = function(user) {
+    user.channel = null;
     // Their socket might already be dead, so wrap in a try-catch
     try {
         user.socket.leave(this.name);