[BUGFIX] Fix crash if form is saved in form_definitions

Classes/XClass/Form/FormEditorController.php

@@ -63,8 +63,8 @@ class FormEditorController extends \TYPO3\CMS\Form\Controller\FormEditorControll
 	 *
 	 * @param string $formPersistenceIdentifier
 	 * @param FormDefinitionArray $formDefinition
-	 * @internal
 	 * @throws \TYPO3\CMS\Core\Cache\Exception\NoSuchCacheException
+	 * @internal
 	 */
 	public function saveFormAction(string $formPersistenceIdentifier, FormDefinitionArray $formDefinition) {
 		$registrationService = $this->objectManager->get(RegisterService::class);
@@ -116,10 +116,16 @@ class FormEditorController extends \TYPO3\CMS\Form\Controller\FormEditorControll
 						sprintf('Could not access storage with uid "%d".', $storageUid)
 					);
 				}
-				$absoluteFilePath = $storage->getFile($fileIdentifier);
+				$absoluteFilePath = PATH_site . $storage->getFile($fileIdentifier)->getPublicUrl();
 			}
 
-			$parsedYaml = Yaml::parse(file_get_contents($absoluteFilePath));
+			try {
+				$parsedYaml = Yaml::parse(file_get_contents($absoluteFilePath));
+			} catch (\Exception $exception) {
+				throw new \InvalidArgumentException(
+					sprintf('Could not access storage "%s".', $absoluteFilePath)
+				);
+			}
 
 			$renderables = self::getFormFieldsRecursive([0 => $parsedYaml]);