Fix decodeAndVerifyHash to have only 2 returns by merging base64 decode and pipe check guards

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/Controller/AttestationController.php

@@ -93,11 +93,7 @@ class AttestationController extends AbstractController
     private function decodeAndVerifyHash(string $hash): ?array
     {
         $decoded = base64_decode(strtr($hash, '-_', '+/'), true);
-        if (!$decoded) {
-            return null;
-        }
-
-        $parts = explode('|', $decoded, 2);
+        $parts = $decoded ? explode('|', $decoded, 2) : [];
         if (2 !== \count($parts)) {
             return null;
         }