RhodeCode CE/EE

Pressing button Remap and Rescan causes 500 with and without "Destroy old data" " Invalidate cache for all repositories" options.

Target repositories directory can be even empty.
With or without changes(new repos added).

OS: Debian 9.9
RHODECODE versions: 4.22.0
RHODECODE license: CE

Exception log:

Exception `TypeError` generated on UTC date: 2020-10-29T07:47:10.580519
Request: POST http://xxx.xxx.xxx.xxx/_admin/settings/mapping/update
yyy.yyy.yyy.yyy Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.111 Safari/537.36

Traceback (most recent call last):
  File "/opt/rhodecode/store/da2il1f83gci4333j0sd256nji9nlhpa-python2.7-pyramid-1.10.4/lib/python2.7/site-packages/pyramid/tweens.py", line 41, in excview_tween
    response = handler(request)
  File "/opt/rhodecode/store/da2il1f83gci4333j0sd256nji9nlhpa-python2.7-pyramid-1.10.4/lib/python2.7/site-packages/pyramid/router.py", line 148, in handle_request
    registry, request, context, context_iface, view_name
  File "/opt/rhodecode/store/da2il1f83gci4333j0sd256nji9nlhpa-python2.7-pyramid-1.10.4/lib/python2.7/site-packages/pyramid/view.py", line 667, in _call_view
    response = view_callable(context, request)
  File "/opt/rhodecode/store/da2il1f83gci4333j0sd256nji9nlhpa-python2.7-pyramid-1.10.4/lib/python2.7/site-packages/pyramid/config/views.py", line 188, in attr_view
    return view(context, request)
  File "/opt/rhodecode/store/da2il1f83gci4333j0sd256nji9nlhpa-python2.7-pyramid-1.10.4/lib/python2.7/site-packages/pyramid/config/views.py", line 214, in predicate_wrapper
    return view(context, request)
  File "/opt/rhodecode/store/da2il1f83gci4333j0sd256nji9nlhpa-python2.7-pyramid-1.10.4/lib/python2.7/site-packages/pyramid/viewderivers.py", line 436, in rendered_view
    result = view(context, request)
  File "/opt/rhodecode/store/da2il1f83gci4333j0sd256nji9nlhpa-python2.7-pyramid-1.10.4/lib/python2.7/site-packages/pyramid/viewderivers.py", line 132, in _class_view
    response = getattr(inst, attr)()
  File "/opt/rhodecode/store/cnpzq6z5xjxzxw2m3d1cfb5yhpazscn5-python2.7-rhodecode-enterprise-ce-4.22.0/lib/python2.7/site-packages/rhodecode/lib/auth.py", line 2507, in local_wrapper
    return wrapper(func, *args, **kwds)
  File "/opt/rhodecode/store/cnpzq6z5xjxzxw2m3d1cfb5yhpazscn5-python2.7-rhodecode-enterprise-ce-4.22.0/lib/python2.7/site-packages/rhodecode/lib/auth.py", line 1823, in __wrapper
    return func(*fargs, **fkwargs)
  File "/opt/rhodecode/store/cnpzq6z5xjxzxw2m3d1cfb5yhpazscn5-python2.7-rhodecode-enterprise-ce-4.22.0/lib/python2.7/site-packages/rhodecode/lib/auth.py", line 2507, in local_wrapper
    return wrapper(func, *args, **kwds)
  File "/opt/rhodecode/store/cnpzq6z5xjxzxw2m3d1cfb5yhpazscn5-python2.7-rhodecode-enterprise-ce-4.22.0/lib/python2.7/site-packages/rhodecode/lib/auth.py", line 1897, in __wrapper
    return func(*fargs, **fkwargs)
  File "/opt/rhodecode/store/cnpzq6z5xjxzxw2m3d1cfb5yhpazscn5-python2.7-rhodecode-enterprise-ce-4.22.0/lib/python2.7/site-packages/rhodecode/lib/auth.py", line 2507, in local_wrapper
    return wrapper(func, *args, **kwds)
  File "/opt/rhodecode/store/cnpzq6z5xjxzxw2m3d1cfb5yhpazscn5-python2.7-rhodecode-enterprise-ce-4.22.0/lib/python2.7/site-packages/rhodecode/lib/auth.py", line 1716, in __wrapper
    return func(*fargs, **fkwargs)
  File "/opt/rhodecode/store/cnpzq6z5xjxzxw2m3d1cfb5yhpazscn5-python2.7-rhodecode-enterprise-ce-4.22.0/lib/python2.7/site-packages/rhodecode/apps/admin/views/settings.py", line 266, in settings_mapping_update
    PermissionModel().trigger_permission_flush()
  File "/opt/rhodecode/store/cnpzq6z5xjxzxw2m3d1cfb5yhpazscn5-python2.7-rhodecode-enterprise-ce-4.22.0/lib/python2.7/site-packages/rhodecode/model/permission.py", line 582, in trigger_permission_flush
    events.trigger(events.UserPermissionsChange(affected_user_ids))
  File "/opt/rhodecode/store/cnpzq6z5xjxzxw2m3d1cfb5yhpazscn5-python2.7-rhodecode-enterprise-ce-4.22.0/lib/python2.7/site-packages/rhodecode/events/__init__.py", line 38, in trigger
    registry.notify(event)
  File "/opt/rhodecode/store/da2il1f83gci4333j0sd256nji9nlhpa-python2.7-pyramid-1.10.4/lib/python2.7/site-packages/pyramid/registry.py", line 109, in notify
    [_ for _ in self.subscribers(events, None)]
  File "/opt/rhodecode/store/x5ng3z8k1rbbxk56dqsa9ri450ka0c4h-python2.7-zope.interface-4.6.0/lib/python2.7/site-packages/zope/interface/registry.py", line 442, in subscribers
    return self.adapters.subscribers(objects, provided)
  File "/opt/rhodecode/store/x5ng3z8k1rbbxk56dqsa9ri450ka0c4h-python2.7-zope.interface-4.6.0/lib/python2.7/site-packages/zope/interface/adapter.py", line 607, in subscribers
    subscription(*objects)
  File "/opt/rhodecode/store/da2il1f83gci4333j0sd256nji9nlhpa-python2.7-pyramid-1.10.4/lib/python2.7/site-packages/pyramid/config/adapters.py", line 101, in derived_subscriber
    return subscriber(arg[0])
  File "/opt/rhodecode/store/cnpzq6z5xjxzxw2m3d1cfb5yhpazscn5-python2.7-rhodecode-enterprise-ce-4.22.0/lib/python2.7/site-packages/rhodecode/apps/_base/subscribers.py", line 45, in trigger_user_permission_flush
    affected_user_ids = set(event.user_ids)
TypeError: 'NoneType' object is not iterable