send callback directly

except this time I'm fixing my own derps instead of @barisusakli

src/categories.js

@@ -93,9 +93,7 @@ var db = require('./database'),
 				category.pageCount = results.pageCount;
 				category.topic_row_size = 'col-md-9';
 
-				plugins.fireHook('filter:category.get', category, uid, function(err, category) {
+				plugins.fireHook('filter:category.get', category, uid, callback);
-					callback(err, category);
-				});
 			});
 		});
 	};