fix: don't die if we can't encode file metadata on upload

Signed-off-by: Robin Appelman <robin@icewind.nl>
Signed-off-by: Carl Schwan <carlschwan@kde.org>

Author: icewind1991

lib/private/FilesMetadata/FilesMetadataManager.php

@@ -160,6 +160,10 @@ public function saveMetadata(IFilesMetadata $filesMetadata): void {
 		}
 
 		$json = json_encode($filesMetadata->jsonSerialize());
+		if (!$json) {
+			$this->logger->error('Failed to json encode file metadata for ' . $filesMetadata->getFileId(), ['metadata' => $filesMetadata->jsonSerialize()]);
+			return;
+		}
 		if (strlen($json) > self::JSON_MAXSIZE) {
 			$this->logger->debug('huge metadata content detected: ' . $json);
 			throw new FilesMetadataException('json cannot exceed ' . self::JSON_MAXSIZE . ' characters long; fileId: ' . $filesMetadata->getFileId() . '; size: ' . strlen($json));