[BUGFIX] Use file name to check extension validity

Instead of using a file's identifier, the file's name is used
to check if it has a valid file extension.

This allows FAL drivers to use non-file name related identifiers.

Change-Id: I5b870e06f60c9259951a5f20fd69660ab19c49c2
Resolves: #57141
Releases: 6.2
Reviewed-on: https://review.typo3.org/28597
Reviewed-by: Frans Saris
Tested-by: Frans Saris
Reviewed-by: Markus Klein
Tested-by: Markus Klein

typo3/sysext/core/Classes/Resource/Filter/FileExtensionFilter.php

@@ -72,7 +72,7 @@ class FileExtensionFilter {
 				$fileReferenceUid = $parts[count($parts) - 1];
 				$fileReference = \TYPO3\CMS\Core\Resource\ResourceFactory::getInstance()->getFileReferenceObject($fileReferenceUid);
 				$file = $fileReference->getOriginalFile();
-				if ($this->isAllowed($file->getIdentifier())) {
+				if ($this->isAllowed($file->getName())) {
 					$cleanValues[] = $value;
 				} else {
 					// Remove the erroneously created reference record again