Merge branch 'security-fix-something-went-wrong-on-when-not-logged-in-ce-12-0' into '12-0-stable'

Return NO_ACCESS if user is nil

See merge request gitlab/gitlabhq!3388

app/models/group.rb

@@ -356,6 +356,8 @@ class Group < Namespace
   end
   def max_member_access_for_user(user)
+    return GroupMember::NO_ACCESS unless user
+
     return GroupMember::OWNER if user.admin?
     members_with_parents