core: fix contest_balloon

packages/hydrooj/package.json

@@ -1,6 +1,6 @@
 {
     "name": "hydrooj",
-    "version": "4.9.26",
+    "version": "4.9.27",
     "bin": "bin/hydrooj.js",
     "main": "src/plugin-api",
     "module": "src/plugin-api",

packages/hydrooj/src/handler/contest.ts

@@ -712,7 +712,7 @@ export class ContestBalloonHandler extends ContestManagementBaseHandler {
             ...todo ? { sent: { $exists: false } } : {},
             ...(!this.tdoc.lockAt || this.user.hasPerm(PERM.PERM_VIEW_CONTEST_HIDDEN_SCOREBOARD))
                 ? {} : { _id: { $lt: this.tdoc.lockAt } },
-        }).sort({ _id: -1 }).project({ uid: 1 }).toArray();
+        }).sort({ _id: -1 }).toArray();
         const uids = bdocs.map((i) => i.uid).concat(bdocs.filter((i) => i.sent).map((i) => i.sent));
         this.response.body = {
             tdoc: this.tdoc,