fix multi-file conversion

the `pt_filename` containst the full path and thus `st_filename` could not be merged with `folder`

convert.py

@@ -82,7 +82,7 @@ def convert_multi(model_id: str, folder: str, token: Optional[str]) -> Conversio
         pt_filename = hf_hub_download(repo_id=model_id, filename=filename, token=token)
 
         sf_filename = rename(pt_filename)
-        sf_filename = os.path.join(folder, sf_filename)
+        sf_filename = os.path.join(folder, os.path.split(sf_filename)[1])
         convert_file(pt_filename, sf_filename)
         local_filenames.append(sf_filename)