fixed update requiring a new backup

src/Controller/SongController.php

@@ -109,7 +109,7 @@ class SongController extends AbstractController
             throw new NotFoundHttpException();
         } else {
             $form = $this->createFormBuilder()
-            ->add('backupPath', FileType::class, ['label' => 'Backup .zip', 'row_attr' => array('class' => 'upload-field'), 'attr' => array('accept' => '.zip')])
+            ->add('backupPath', FileType::class, ['label' => 'Backup .zip', 'required' => false, 'row_attr' => array('class' => 'upload-field'), 'attr' => array('accept' => '.zip')])
             ->add('tags', TextType::class, ['label' => 'Tags', 'row_attr' => array('class' => 'tags-field'), 'required' => false, 'data' => $song->getTags()])
             ->add('isExplicit', CheckboxType::class, ['label' => 'Is the song explicit?', 'row_attr' => array('class' => "tags-field"), 'required' => false, 'data' => $song->getIsExplicit()])
             ->add('save', SubmitType::class, ['label' => 'Upload'])