core: fix problem_create langs

packages/hydrooj/src/handler/problem.ts

@@ -991,6 +991,7 @@ export class ProblemStatisticsHandler extends ProblemDetailHandler {
 
 export class ProblemCreateHandler extends Handler {
     async get() {
+        this.response.body.statementLangs = this.ctx.i18n.langs(false);
         this.response.template = 'problem_edit.html';
         this.response.body = {
             page_name: 'problem_create',