Add null NSString proctection.

@@ -633,19 +633,19 @@
             }];
         }
     }else {
-        [YH_RoomSecretViewController showInController:self completionBlock:^(NSDictionary *dic, BOOL success) {
+        [YH_RoomSecretViewController showInController:self completionBlock:^(NSDictionary *obj, BOOL success) {
            
             if (success) {
                 YH_ChannelModel *model = [YH_ChannelModel new];
-                model.roomTitle = dic[@"name"];
-                model.roomURL = dic[@"url"];
-                model.channel_id = dic[@"channel_id"];
-                model.cid = dic[@"cid"];
-                model.app = dic[@"app"];
-                model.type = dic[@"type"];
-                model.room = dic[@"id"];
-                model.title = dic[@"title"];
-                model.secret = dic[@"secret"];
+                model.roomTitle = IsNilOrNull(obj[@"name"])?@"":obj[@"name"];
+                model.roomURL = IsNilOrNull(obj[@"url"])?@"":obj[@"url"];
+                model.channel_id = IsNilOrNull(obj[@"channel_id"])?@"":obj[@"channel_id"];
+                model.cid = IsNilOrNull(obj[@"cid"])?@"":obj[@"cid"];
+                model.app = IsNilOrNull(obj[@"app"])?@"":obj[@"app"];
+                model.type = IsNilOrNull(obj[@"type"])?@"":obj[@"type"];
+                model.room = IsNilOrNull(obj[@"id"])?@"":obj[@"id"];
+                model.title = IsNilOrNull(obj[@"title"])?@"":obj[@"title"];
+                model.secret = IsNilOrNull(obj[@"secret"])?@"":obj[@"secret"];
                 
                 _currentChannel = model;