delete tag if it has no topics left

src/controllers/tags.js

@@ -18,6 +18,9 @@ tagsController.getTag = function(req, res, next) {
 				return next(err);
 			}
 			data.tag = tag;
+			if (data.topics && !data.topics.length) {
+				topics.deleteTag(tag);
+			}
 			res.render('tag', data);
 		});
 	});

src/topics/tags.js

@@ -27,6 +27,11 @@ module.exports = function(Topics) {
 		db.sortedSetCard('tag:' + tag + ':topics', callback);
 	};
 
+	Topics.deleteTag = function(tag) {
+		db.delete('tag:' + tag + ':topics');
+		db.setRemove('tags', tag);
+	};
+
 	Topics.getTags = function(callback) {
 		db.getSetMembers('tags', callback);
 	};