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

@@ -528,9 +528,13 @@ var Client = (function () {
 					if (err) {
 						callback(err);
 						reject(err);
+					} else {
+						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

@@ -541,9 +541,13 @@ class Client {
 					if (err) {
 						callback(err);
 						reject(err);
+					} else {
+						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){