forgot err, thanks @barisusakli

src/categories.js

@@ -94,7 +94,7 @@ var db = require('./database'),
 				category.topic_row_size = 'col-md-9';
 
 				plugins.fireHook('filter:category.get', category, uid, function(err, category) {
-					callback(null, category);
+					callback(err, category);
 				});
 			});
 		});