core: 修复problem_edit中dump出错问题

packages/hydrooj/package.json

@@ -1,6 +1,6 @@
 {
     "name": "hydrooj",
-    "version": "2.13.3",
+    "version": "2.13.4",
     "bin": "bin/hydrooj.js",
     "main": "dist/loader.js",
     "typings": "dist/loader.d.ts",

packages/hydrooj/src/handler/problem.ts

@@ -347,8 +347,8 @@ class ProblemSettingsHandler extends ProblemManageHandler {
             [this.pdoc.title, 'problem_detail', { pid }, true],
             ['problem_settings', null],
         ];
-        if (this.response.body.config) {
-            this.response.body.config = yaml.safeDump(this.response.body.config);
+        if (this.response.body.pdoc.config) {
+            this.response.body.pdoc.config = yaml.safeDump(this.response.body.pdoc.config);
         }
     }