Fix dmesh importer error

[hideeehst]

Fix this error:

Python: Traceback (most recent call last):
  File "~/.config/blender/3.5/scripts/addons/HaydeeTools/haydee_importer/import_dmesh.py", line 416, in execute
    read_dmesh(self, context, os.path.join(self.directory, filepath),
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen posixpath>", line 90, in join
  File "<frozen genericpath>", line 152, in _check_arg_types
TypeError: join() argument must be str, bytes, or os.PathLike object, not 'OperatorFileListElement'