Safeguards last_commit access in Huggingface files

It seems the `last_commit` is not always returned by the API when
browsing files in the Huggingface repository. This ensures that even
if the 'last_commit' is None or absent, the files are correctly listed,
although without date or timestamp.

Author: davelopez

lib/galaxy/files/sources/huggingface.py

@@ -104,7 +104,7 @@ def _to_filesystem_path(self, path: str) -> str:
 
     def _extract_timestamp(self, info: dict) -> Optional[str]:
         """Extract timestamp from Hugging Face file info to use it in the RemoteFile entry."""
-        last_commit: dict = info.get("last_commit", {})
+        last_commit: dict = info.get("last_commit") or {}
         return last_commit.get("date")
 
     def _get_file_hashes(self, info: dict) -> Optional[list[RemoteFileHash]]: