Error 500 on sign-in page after update from 12.9.2 to 12.10

After Upgrading from 12.9.2 to 12.10 the login page shows a error 500 Setup: OS=Ubuntu 16.04 RAM=4GB CPU=2 Cores We installed all previous updates without any issues.

Output from gitlab-ctl tail:

`{"method":"GET","path":"/users/sign_in","format":"html","controller":"SessionsController","action":"new","status":500,"time":"2020-04-24T09:08:40.327Z","params":[],"remote_ip":"192.168.133.221","user_id":null,"username":null,"ua":"Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:75.0) Gecko/20100101 Firefox/75.0","queue_duration_s":null,"redis_calls":12,"redis_duration_s":0.01,"correlation_id":"br9TwrEPbM6","cpu_s":0.19,"exception.class":"ActionView::Template::Error","exception.message":"undefined method `include?' for nil:NilClass","exception.backtrace":["app/helpers/explore_helper.rb:55:in `public_visibility_restricted?'","app/views/layouts/devise.html.haml:41","app/controllers/application_controller.rb:125:in `render'","app/controllers/sessions_controller.rb:50:in `new'","app/controllers/application_controller.rb:479:in `set_current_admin'","lib/gitlab/session.rb:11:in `with_session'","app/controllers/application_controller.rb:470:in `set_session_storage'","app/controllers/application_controller.rb:464:in `set_locale'","lib/gitlab/error_tracking.rb:48:in `with_context'","app/controllers/application_controller.rb:559:in `sentry_context'","lib/gitlab/application_context.rb:52:in `block in use'","lib/gitlab/application_context.rb:52:in `use'","lib/gitlab/application_context.rb:20:in `with_context'","app/controllers/application_controller.rb:455:in `set_current_context'"],"db_duration_s":0.0,"view_duration_s":0.0,"duration_s":0.14}`

Could you let me know what to do to remove this error.

Thank you!