AttributeError: 'NoneType' object has no attribute 'first_name'

hi everyone,
my bench was running but UI not open it shown
Traceback (most recent call last):
File “/home/ubuntu/frappe-bench/apps/frappe/frappe/”, line 59, in application
File “/home/ubuntu/frappe-bench/apps/frappe/frappe/”, line 121, in init_request
frappe.local.http_request = frappe.auth.HTTPRequest()
File “/home/ubuntu/frappe-bench/apps/frappe/frappe/”, line 53, in init
frappe.local.login_manager = LoginManager()
File “/home/ubuntu/frappe-bench/apps/frappe/frappe/”, line 120, in init
File “/home/ubuntu/frappe-bench/apps/frappe/frappe/”, line 146, in set_user_info
self.full_name = " ".join(filter(None, [,
AttributeError: ‘NoneType’ object has no attribute ‘first_name’

Explain the issue in detail please.

thanks for reply,
Bench running successfully but UI not open don’t know what’s the reason it shown error trace back above