Update src/Form/FormArrayFactory.php

Co-authored-by: jensschuppe <jensschuppe@users.noreply.github.com>

Author: dontub

src/Form/FormArrayFactory.php

@@ -53,17 +53,9 @@ public function createFormArray(DefinitionInterface $definition, FormStateInterf
           $formState->set(['form', $definition->getPropertyFormName()], $form);
         }
 
-        if (is_array($definition->getOptionsValue('cssClasses'))
-          && [] !== $definition->getOptionsValue('cssClasses')
-        ) {
-          // @phpstan-ignore offsetAccess.nonOffsetAccessible
-          $form['#attributes']['class'] ??= [];
-          $form['#attributes']['class'] = [
-            // @phpstan-ignore arrayUnpacking.nonIterable
-            ...$form['#attributes']['class'],
-            ...$definition->getOptionsValue('cssClasses'),
-          ];
-        }
+        $form['#attributes']['class'] =
+          ($definition->getOptionsValue('cssClasses') ?? [])
+          + ($form['#attributes']['class'] ?? []);
 
         return $form;
       }