core: fix problem_copy testdata link

packages/hydrooj/package.json

@@ -1,6 +1,6 @@
 {
     "name": "hydrooj",
-    "version": "3.10.4",
+    "version": "3.10.5",
     "bin": "bin/hydrooj.js",
     "main": "src/loader",
     "module": "src/loader",

packages/hydrooj/src/handler/problem.ts

@@ -558,6 +558,7 @@ export class ProblemFilesHandler extends ProblemDetailHandler {
     @post('type', Types.Range(['testdata', 'additional_file']), true)
     async postGetLinks(domainId: string, files: Set<string>, type = 'testdata') {
         if (type === 'testdata' && !this.user.own(this.pdoc)) {
+            if (this.pdoc.reference) throw new BadRequestError('Cannot download testdata.');
             if (!this.user.hasPriv(PRIV.PRIV_READ_PROBLEM_DATA)) this.checkPerm(PERM.PERM_READ_PROBLEM_DATA);
             if (this.tdoc && !contest.isDone(this.tdoc)) throw new ContestNotEndedError(this.tdoc.domainId, this.tdoc.docId);
         }