Double assertion with if clause to satisfy phpstan in tests

tests/MDPlausiForLegalStatusTest.php

@@ -145,6 +145,10 @@ public function testCreatorsInCopyrightCollectiveAsksForRestrictedLicense():void
         self::assertEquals(MDPlausiLegalCheckResultType::expect_restricted_legal_status, $warningStatus['msgs'][0]['type']);
 
         self::assertArrayHasKey('additional', $warningStatus['msgs'][0]);
+        // For phpstan
+        if (empty($warningStatus['msgs'][0]['additional'])) {
+            throw new Exception("Output array should have key 'additional'");
+        }
         self::assertEquals(MDCopyrightCollective::vg_bildkunst, $warningStatus['msgs'][0]['additional']['representation']);
 
     }