In the case when a user can and has authenticated with ldap, however

ldap is disabled in the gitlab config, this fixes the API still calling
the ldap backend.

lib/api/internal.rb

@@ -35,7 +35,9 @@ module API
           user = key.user
 
           return false if user.blocked?
+          if Gitlab.config.ldap.enabled
             return false if user.ldap_user? && Gitlab::LDAP::User.blocked?(user.extern_uid)
+          end
 
           action = case git_cmd
                    when *DOWNLOAD_COMMANDS