judge: fix initial run

packages/hydrojudge/package.json

@@ -1,7 +1,7 @@
 {
     "name": "@hydrooj/hydrojudge",
     "bin": "bin/hydrojudge.js",
-    "version": "2.2.2",
+    "version": "2.2.3",
     "main": "package.json",
     "author": "undefined <i@undefined.moe>",
     "repository": "https://github.com/hydro-dev/Hydro.git",

packages/hydrojudge/src/judge/run.ts

@@ -58,7 +58,7 @@ export const judge = async (ctx) => {
     if (filename) copyIn[`${filename}.in`] = { content: ctx.config.input };
     const copyOut = filename ? [`${filename}.out`] : [];
     const stdin = path.resolve(ctx.tmpdir, '0.in');
-    await fs.writeFile(stdin, ctx.config.input);
+    await fs.writeFile(stdin, ctx.config.input || '');
     const stdout = path.resolve(ctx.tmpdir, '0.out');
     const stderr = path.resolve(ctx.tmpdir, '0.err');
     const res = await run(