修复学生端不可用问题

frontend/student/dashboard.php

@@ -393,6 +393,7 @@ include __DIR__ . '/../includes/header.php';
     async function loadHomework() {
         try {
             const res = await apiGet(`/api/student/homework/${STUDENT_ID}`);
+            let html = '';
             if (res && res.success) {
                 res.data.homework.forEach(record => {
                     const pointsClass = record.points_change > 0 ? 'plus' : 'minus';
@@ -410,7 +411,6 @@ include __DIR__ . '/../includes/header.php';
                 if (res.data.homework.length === 0) {
                     html = '<tr><td colspan="5" style="text-align:center;">暂无作业扣分记录</td></tr>';
                 }
-                }
                 document.getElementById('homeworkList').innerHTML = html;
             }
         } catch (error) {