fix: 修复eval参加状态bug

src/views/CoursePage/tabs/TaskTab.vue

@@ -62,10 +62,10 @@
           </el-tag>
           <el-row v-if="task['examId']" class="timeline-content">
             <el-tag v-if="this.state(task)==='NOT_STARTED'" size="small" >未开始</el-tag>
-            <el-tag v-else-if="this.state(task)==='RUNNING' && task['joined']" size="small" type="success">
+            <el-tag v-else-if="this.state(task)==='RUNNING' && task['isJoined']" size="small" type="success">
               已参加
             </el-tag>
-            <el-tag v-else-if="this.state(task)==='RUNNING' && !task['joined']" size="small">未参加</el-tag>
+            <el-tag v-else-if="this.state(task)==='RUNNING' && !task['isJoined']" size="small">未参加</el-tag>
             <el-tag v-else-if="this.state(task)==='FINISHED'" size="small" type="info">已结束</el-tag>
             <el-tag v-else-if="this.state(task)==='CLOSED'" size="small" type="info">已关闭</el-tag>
           </el-row>