ui: add submission language not available warning

packages/ui-default/locales/zh.yaml

@@ -560,6 +560,7 @@ No Permission to Create a Discussion: 您没有权限创建讨论
 No Permission to Submit: 您没有权限递交
 No problem.: 没有题目。
 No solutions so far...: 目前还没有题解...
+No submission language available for this problem.: 本题没有可用的提交语言。
 No Submissions: 没有递交
 No target available: 无可用目标
 No testcase here: 此处没有测试点
@@ -577,9 +578,9 @@ objective: 客观题
 Oh, the user doesn't have any contributions!: 啊哦，这个用户还没贡献过题目~
 Oh, the user hasn't created any discussions yet!: 这个用户还没有发布过讨论
 Oh, the user hasn't submitted yet!: 这个用户还没有交过题 _(:зゝ∠)_
+Oh, there are no tasks that match the filter!: 喔，目前没有符合过滤条件的任务。
 Oh, there is no submission!: 喔，还没有评测记录呢！
 Oh, there is no task in the queue!: 喔，队列中目前没有任务。
-Oh, there are no tasks that match the filter!: 喔，目前没有符合过滤条件的任务。
 Ok: 确定
 Only A-Z, a-z, 0-9 and _ are accepted: 只接受 A-Z, a-z, 0-9 和 _
 Oops, there are no results.: 呀，没有结果。

packages/ui-default/templates/partials/problem_description.html

@@ -9,6 +9,11 @@
       <p>{{ pdoc.config }}</p>
     </blockquote>
   {% endif %}
+  {% if pdoc.config.langs and not pdoc.config.langs|length %}
+    <blockquote class="warn">
+      <p>{{ _('No submission language available for this problem.') }}</p>
+    </blockquote>
+  {% endif %}
   {% if tdoc and tdoc.docType == model.document.TYPE_CONTEST and model.contest.isDone(tdoc) %}
     <blockquote class="note">
       <p>{{ _('You cannot submit for this problem because the contest is ended. You can click "Open in Problem Set" to view this problem in normal mode.') }}</p>