judge: 修复测试数据更新无效的问题

packages/hydrojudge/package.json

@@ -1,7 +1,7 @@
 {
     "name": "@hydrooj/hydrojudge",
     "bin": "bin/hydrojudge.js",
-    "version": "2.1.18",
+    "version": "2.1.19",
     "main": "package.json",
     "author": "masnn",
     "repository": "https://github.com/hydro-dev/Hydro.git",

packages/hydrojudge/src/service.ts

@@ -207,7 +207,7 @@ async function postInit() {
                 this.domainId = this.request.domainId;
                 this.lang = this.request.lang;
                 this.code = this.request.code;
-                this.data = this.request.data;
+                this.data = this.request.data.toString();
                 this.config = this.request.config;
                 this.next = getNext(this);
                 this.end = getEnd(this.domainId, this.rid);