Fix saving new problems with statements

Fixes #2646.

We used to persist the entity both before and after calling the lifecycle callbacks ourselves, which would introduce weird behavior where Doctrine wanted to insert some rows twice.
By not persisting before calling the callbacks ourselves, this issue goes away.

(cherry picked from commit 9f12b77)

Author: nickygerritsen

ChangeLog

@@ -1,5 +1,9 @@
 DOMjudge Programming Contest Judging System
 
+Version 8.3.2
+---------------------------
+ - Fix saving new problems with problem statement from web UI.
+
 Version 8.3.1 - 21 July 2024
  - Create autoload_runtime.php as normal user to prevent a composer warning.
 

webapp/src/Controller/Jury/ProblemController.php

@@ -1087,7 +1087,6 @@ public function addAction(Request $request): Response
         $form->handleRequest($request);
 
         if ($form->isSubmitted() && $form->isValid()) {
-            $this->em->persist($problem);
             $this->saveEntity($this->em, $this->eventLogService, $this->dj, $problem, null, true);
             return $this->redirectToRoute('jury_problem', ['probId' => $problem->getProbid()]);
         }