patches from zhengzhou site

packages/hydrooj/src/handler/contest.ts

@@ -333,7 +333,7 @@ export class ContestProblemListHandler extends ContestDetailBaseHandler {
         await this.limitRate('add_discussion', 3600, 60);
         await contest.addClarification(domainId, tid, this.user._id, content, this.request.ip, subject);
         if (!this.user.own(this.tdoc)) {
-            await message.send(1, this.tdoc.maintainer.concat(this.tdoc.owner), JSON.stringify({
+            await message.send(1, (this.tdoc.maintainer || []).concat(this.tdoc.owner), JSON.stringify({
                 message: 'Contest {0} has a new clarification about {1}, please go to contest clarifications page to reply.',
                 params: [this.tdoc.title, subject > 0 ? `#${this.tdoc.pids.indexOf(subject) + 1}` : 'the contest'],
                 url: this.url('contest_clarification', { tid }),