AttributeError: 'PurchaseInvoice' object has no attribute '_seen'

New problem…any solution to this error?

Traceback (most recent call last):
File “/home/frappe/frappe-bench/apps/frappe/frappe/app.py”, line 62, in application
response = frappe.handler.handle()
File “/home/frappe/frappe-bench/apps/frappe/frappe/handler.py”, line 22, in handle
data = execute_cmd(cmd)
File “/home/frappe/frappe-bench/apps/frappe/frappe/handler.py”, line 53, in execute_cmd
return frappe.call(method, **frappe.form_dict)
File “/home/frappe/frappe-bench/apps/frappe/frappe/init.py”, line 939, in call
return fn(*args, **newargs)
File “/home/frappe/frappe-bench/apps/frappe/frappe/desk/form/load.py”, line 52, in getdoc
doc.add_seen()
File “/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py”, line 1120, in add_seen
if self._seen:
AttributeError: ‘PurchaseInvoice’ object has no attribute ‘_seen’