Uploading stock opening balance

Hi,
I have the down message while I was uploading the stock opening balance .
I appreciate if some one can help to solve this issue.

thanks
Ahmad

Traceback (most recent call last):
File “/home/frappe/benches/bench-2018-10-31/apps/frappe/frappe/core/doctype/data_import/importer.py”, line 395, in upload
doc.insert()
File “/home/frappe/benches/bench-2018-10-31/apps/frappe/frappe/model/document.py”, line 220, in insert
self._validate_links()
File “/home/frappe/benches/bench-2018-10-31/apps/frappe/frappe/model/document.py”, line 719, in _validate_links
result = d.get_invalid_links(is_submittable=self.meta.is_submittable)
File “/home/frappe/benches/bench-2018-10-31/apps/frappe/frappe/model/base_document.py”, line 464, in get_invalid_links
setattr(self, df.fieldname, values.name)
AttributeError: ‘NoneType’ object has no attribute ‘name’