fix: extract file descriptor when items have nested 'file' key

When the frontend sends multiple files via 'Choose from Files',
each item in the files array has the shape:
  { file: { path: '...' }, name: 'filename' }

processFileData() was passing the whole item as 'file' to
getNodeFromData(), creating a double-nested file.file.path
structure that getNodeFromData() cannot resolve, triggering
the 'No file source provided' exception.

Fix: extract fileData['file'] if present, otherwise fall back
to using fileData itself as the descriptor.

Fixes #7343

Signed-off-by: Vitor Mattos <1079143+vitormattos@users.noreply.github.com>

Author: vitormattos

lib/Service/RequestSignatureService.php

@@ -220,7 +220,7 @@ private function processFileData(array $fileData, ?IUser $userManager, array $se
 			$sourceNode = $this->fileService->getNodeFromData([
 				'userManager' => $userManager,
 				'name' => $name,
-				'file' => $fileData,
+				'file' => $fileData['file'] ?? $fileData,
 				'settings' => $settings,
 			]);
 		}