Add check for empty title, fix tag filter paginate

modules/contest.js

@@ -87,6 +87,7 @@ app.post('/contest/:id/edit', async (req, res) => {
       contest.ranklist_id = ranklist.id;
     }
 
+    if (!req.body.trim()) throw new ErrorMessage('比赛名不能为空。');
     contest.title = req.body.title;
     if (!Array.isArray(req.body.problems)) req.body.problems = [req.body.problems];
     contest.problems = req.body.problems.join('|');

modules/problem.js

@@ -107,7 +107,7 @@ app.get('/problems/tag/:tagIDs', async (req, res) => {
     }
 
     let paginate = syzoj.utils.paginate(await Problem.count(sql), req.query.page, syzoj.config.page.problem);
-    let problems = await Problem.query(sql);
+    let problems = await Problem.query(sql + paginate.toSQL());
 
     await problems.forEachAsync(async problem => {
       problem.allowedEdit = await problem.isAllowedEditBy(res.locals.user);
@@ -256,6 +256,7 @@ app.post('/problem/:id/edit', async (req, res) => {
       }
     }
 
+    if (!req.body.trim()) throw new ErrorMessage('题目名不能为空。');
     problem.title = req.body.title;
     problem.description = req.body.description;
     problem.input_format = req.body.input_format;
@@ -344,6 +345,7 @@ app.post('/problem/:id/import', async (req, res) => {
 
     if (!json.success) throw new ErrorMessage('题目加载失败。', null, json.error);
 
+    if (!json.obj.trim()) throw new ErrorMessage('题目名不能为空。');
     problem.title = json.obj.title;
     problem.description = json.obj.description;
     problem.input_format = json.obj.input_format;

utility.js

@@ -270,7 +270,11 @@ module.exports = {
     return {
       currPage: currPage,
       perPage: perPage,
-      pageCnt: pageCnt
+      pageCnt: pageCnt,
+      toSQL: () => {
+        if (!pageCnt) return '';
+        else return ` LIMIT ${(currPage - 1) * perPage},${perPage}`
+      }
     };
   },
   removeTitleTag(s) {