Join Server returns server properly

Previously if the client was already part of a server and attempted to
accept an invite to it again, it would stall and not work correctly.

lib/Client.js

@@ -529,7 +529,11 @@ var Client = (function () {
 						callback(err);
 						reject(err);
 					} else {
-						self.serverCreateListener.set(res.body.guild.id, [resolve, callback]);
+						if (self.getServer("id", res.body.guild.id)) {
+							resolve(self.getServer("id", res.body.guild.id));
+						} else {
+							self.serverCreateListener.set(res.body.guild.id, [resolve, callback]);
+						}
 					}
 				});
 			});

lib/channel.js

@@ -19,7 +19,7 @@ var Channel = (function () {
     _createClass(Channel, [{
         key: "equals",
         value: function equals(object) {
-            return object.id === this.id;
+            return object && object.id === this.id;
         }
     }, {
         key: "addMessage",

src/Client.js

@@ -542,7 +542,11 @@ class Client {
 						callback(err);
 						reject(err);
 					} else {
-						self.serverCreateListener.set(res.body.guild.id, [resolve, callback]);
+						if (self.getServer("id", res.body.guild.id)) {
+							resolve(self.getServer("id", res.body.guild.id));
+						} else {
+							self.serverCreateListener.set(res.body.guild.id, [resolve, callback]);
+						}
 					}
 				});
 

src/channel.js

@@ -14,7 +14,7 @@ class Channel {
     }
 
     equals(object) {
-        return object.id === this.id;
+        return (object && object.id === this.id);
     }
     
     addMessage(data){