ERPNext 13.x generates Error Log with title - frappe.core.doctype.user.user.create_contact

Hello,

Sometimes ERPNext show a message regarding Error Log.

On checking Error Log I found that there are 3 entries. Each entries Title is - frappe.core.doctype.user.user.create_contact and Error details are

Traceback (most recent call last):
  File "apps/frappe/frappe/utils/background_jobs.py", line 134, in execute_job
    method(**kwargs)
  File "apps/frappe/frappe/core/doctype/user/user.py", line 1129, in create_contact
    contact.insert(
  File "apps/frappe/frappe/model/document.py", line 255, in insert
    self._validate_links()
  File "apps/frappe/frappe/model/document.py", line 908, in _validate_links
    frappe.throw(_("Could not find {0}").format(msg), frappe.LinkValidationError)
  File "apps/frappe/frappe/__init__.py", line 504, in throw
    msgprint(
  File "apps/frappe/frappe/__init__.py", line 479, in msgprint
    _raise_exception()
  File "apps/frappe/frappe/__init__.py", line 434, in _raise_exception
    raise raise_exception(msg)

What is the reason for generation of this Error Log?

TIA

Yogi Yang