fix: 컨텐츠 없을 때 에러 발생하는 문제 해결

frontend/src/components/Article/ArticlePreview/ArticlePreview.jsx

@@ -13,7 +13,7 @@ export default function ArticlePreview({ to, title, contents = [] }) {
         <RightIcon />
       </Link>
       <div className={styles.main}>
-        {contents.map((content) => {
+        {contents.map?.((content) => {
           return (
             <Link
               to={`${to}/${content.id}`}

frontend/src/components/ChatRoom/ChatRoom.jsx

@@ -14,7 +14,7 @@ export default function ChatRoom() {
         className={styles.messageList}
         ref={chatListRef}
       >
-        {messages.map((message) => (
+        {messages.map?.((message) => (
           <li
             key={message.id}
             className={message.isMine ? styles.my : styles.your}

frontend/src/components/ChatRoom/ChatRoom.module.css

@@ -11,7 +11,6 @@
 .title {
   margin: 0;
   padding: 16px;
-  z-index: 9;
 }
 
 .messageList {
@@ -97,7 +96,6 @@
   border-radius: 12px;
   box-shadow: var(--shadow);
   overflow: hidden;
-  z-index: 9;
 
   & > input[type='text'] {
     flex: 1;

frontend/src/pages/LearningLecturesPage/LearningLecturesPage.jsx

@@ -14,7 +14,7 @@ export default function LearningLecturesPage() {
     <section>
       <h2 className={styles.title}>수강중인 강의</h2>
       <div className={styles.grid}>
-        {onGoingClasses.map((lecture) => (
+        {onGoingClasses.map?.((lecture) => (
           <Link
             key={lecture.lecture_id}
             to={`/lecture/${lecture.lecture_id}`}

frontend/src/pages/NoticeListPage/NoticeListPage.jsx

@@ -13,7 +13,7 @@ export default function NoticeListPage() {
       title="공지사항"
       canCreate={false}
     >
-      {notices?.map((notice) => (
+      {notices?.map?.((notice) => (
         <ArticleLink
           key={`${notice.id}`}
           title={notice.title}

frontend/src/pages/QuestionListPage/QuestionListPage.jsx

@@ -13,7 +13,7 @@ export default function QuestionListPage() {
       title="Q&A"
       canCreate={true}
     >
-      {questions.map((question) => (
+      {questions.map?.((question) => (
         <ArticleLink
           key={`${question.title}${question.createtAt}`}
           title={question.title}

frontend/src/pages/StudentHomePage/StudentHomePage.jsx

@@ -13,12 +13,12 @@ export default function StudentHomePage() {
   };
 
   const { data } = useLectures();
-  const allClasses = data?.data;
+  const allClasses = data?.data ?? [];
 
   return (
     <MaxWidthLayout>
       <ClassGrid title="수강중인 강의">
-        {onGoingClasses.map((lecture) => (
+        {onGoingClasses.map?.((lecture) => (
           <ClassCard
             key={lecture.lecture_id}
             path={`/lecture/${lecture.lecture_id}`}
@@ -28,7 +28,7 @@ export default function StudentHomePage() {
         ))}
       </ClassGrid>
       <ClassGrid title="전체 강의">
-        {allClasses?.map((lecture) => (
+        {allClasses.map?.((lecture) => (
           <ClassCard
             key={lecture.id}
             path={`/lecture/${lecture.id}/info`}

frontend/src/pages/StudentListPage/StudentListPage.jsx

@@ -14,7 +14,7 @@ export default function StudentListPage() {
 
   return (
     <ArticleBoard title="수강생 관리">
-      {students.map((student) => {
+      {students.map?.((student) => {
         return (
           <ArticleLink
             key={`${student.name}${student.sub}`}

frontend/src/pages/TeacherNoticeListPage/TeacherNoticeListPage.jsx

@@ -16,7 +16,7 @@ export default function TeacherNoticeListPage() {
       title="공지사항"
       canCreate={true}
     >
-      {notices.map((notice) => {
+      {notices.map?.((notice) => {
         if (notice.sub && notice.title) {
           return (
             <ArticleLink