Validator returns 500 instead of 404

[glenrobson]

On the live version the validator is returning 500 rather than a 404 for the following (including call counts:

 1 /. 500
   1 /Nmap/folder/check1536524256 500
   1 /Nmap/folder/check1536828751 500
   1 /Yealink-T28P/Y000000000000.cfg 500
   1 /Yealink-T28P/Y000000000005.cfg 500
   1 /Yealink-T28P/Y000000000007.cfg 500
   1 /Yealink/T28P/y000000000000.cfg 500
   1 /Yealink/T28P/y000000000004.cfg 500
   1 /Yealink/T28P/y000000000005.cfg 500
   1 /Yealink/T28P/y000000000007.cfg 500
   1 /YealinkT28P/Y000000000000.cfg 500
   1 /YealinkT28P/Y000000000005.cfg 500
   1 /YealinkT28P/Y000000000007.cfg 500
   1 /dms/Yealink-T28P/Y000000000000.cfg 500
   1 /dms/Yealink-T28P/Y000000000005.cfg 500
   1 /dms/Yealink-T28P/Y000000000007.cfg 500
   1 /dms/Yealink/T28P/y000000000000.cfg 500
   1 /dms/Yealink/T28P/y000000000004.cfg 500
   1 /dms/Yealink/T28P/y000000000005.cfg 500
   1 /dms/Yealink/T28P/y000000000007.cfg 500
   1 /dms/YealinkT28P/Y000000000000.cfg 500
   1 /dms/YealinkT28P/Y000000000005.cfg 500
   1 /dms/YealinkT28P/Y000000000007.cfg 500
   1 /evox/about 500
   1 /p/m/a/scripts/setup.php 500
   1 /phpMyAdmin-2.10.0/scripts/setup.php 500
   1 /phpmyadm1n/index.php 500
   1 /polycom/000000000000.cfg 500
   1 /v/index.php 500
   1 /webdb/scripts/setup.php 500
   1 /yealink/T41P/y000000000036.cfg 500
   1 [13/Sep/2018:09:12:08 "GET
   2 "GET HTTP/1.1"
   2 +0000] /region_pixels?version=2.0&server=api.bl.uk&prefix=image%2Fiiif&identifier=ark%3A%2F81055%2Fvdc_100038478811.0x000001&t=1534464000000
   2 /YealinkT28P/Y000000000004.cfg 500
   2 /data/admin/ver.txt 500
   2 /data/admin/verifies.txt 500
   2 /dms/YealinkT28P/Y000000000004.cfg 500
   2 /graphs/ 500
   2 /myAdmin/scripts/setup.php 500
   2 /mysqladmin/scripts/setup.php 500
   2 /phpmanager/scripts/setup.php 500
   2 /sdk 500
   2 /sqladm/scripts/setup.php 500
   2 /v3.0/web/assets/css/site.css 500
   3 /1hou.php 500
   3 /english/ 500
   3 /mysql/scripts/setup.php 500
   3 /user/register/ 500
   4 /.well-known/security.txt 500
   4 /1.php 500
   4 /2.php 500
   4 /phpAdmin/index.php 500
   4 /phpMyAdmin/scripts/db___.init.php 500
   4 /phpmyadmin/scripts/db___.init.php 500
   4 /qaz.php 500
   4 /tomcat.php 500
   4 /uuu.php 500
   5 /MyAdmin/scripts/setup.php 500
   5 /blog//wp-login.php 500
   5 /myadmin/scripts/setup.php 500
   6 /pc/account/login.aspx 500
   6 /pma/scripts/setup.php 500
   6 /wordpress//wp-login.php 500
   6 /wp//wp-login.php 500
   8 /scripts/setup.php 500
  12 /phpMyAdmin/scripts/setup.php 500
  14 /phpmyadmin/scripts/setup.php 500
  16 /caonma.php 500
  16 /qw.php 500
  17 /ss.php 500
  17 /wcp.php 500
  19 /l6.php 500
  20 /boots.php 500
  20 /miao.php 500
  20 /she.php 500
  22 /manager/html 500
  23 /myadmin2/index.php 500
  23 /mysqladmin/index.php 500
  23 /phpMyAdmin/index.php 500
  23 /phpmyadmin/index.php 500
  23 /phpmyadmin2/index.php 500
  23 /pmd/index.php 500
  23 /tools/phpMyAdmin/index.php 500
  23 /web/phpMyAdmin/index.php 500
  24 /PMA/index.php 500
  24 /PMA2/index.php 500
  24 /admin/PMA/index.php 500
  24 /admin/index.php 500
  24 /admin/mysql/index.php 500
  24 /admin/mysql2/index.php 500
  24 /admin/phpMyAdmin/index.php 500
  24 /admin/phpmyadmin/index.php 500
  24 /admin/phpmyadmin2/index.php 500
  24 /admin/pma/index.php 500
  24 /claroline/phpMyAdmin/index.php 500
  24 /db/index.php 500
  24 /dbadmin/index.php 500
  24 /myadmin/index.php 500
  24 /mysql-admin/index.php 500
  24 /mysql/index.php 500
  24 /phpMyAdmin.old/index.php 500
  24 /phpMyAdmin/phpMyAdmin/index.php 500
  24 /phpMyAdminold/index.php 500
  24 /phpMyadmin_bak/index.php 500
  24 /phpadmin/index.php 500
  24 /phpma/index.php 500
  24 /phpmyadmin-old/index.php 500
  24 /phpmyadmin/phpmyadmin/index.php 500
  24 /phpmyadmin0/index.php 500
  24 /phpmyadmin1/index.php 500
  24 /pma-old/index.php 500
  24 /pma/index.php 500
  24 /pmamy/index.php 500
  24 /pmamy2/index.php 500
  24 /typo3/phpmyadmin/index.php 500
  24 /www/phpMyAdmin/index.php 500
  24 /xampp/phpmyadmin/index.php 500
  27 /zshmindex.php 500
  27 /zuoindex.php 500
  28 /ceshi.php 500
  28 /linuxse.php 500
  28 /xz.php 500
  29 /app.php 500
  29 /default.php 500
  29 /help.php 500
  29 /hh.php 500
  29 /python.php 500
  29 /sean.php 500
  29 /tiandi.php 500
  30 /9510.php 500
  30 /aaaa.php 500
  30 /angge.php 500
  30 /aw.php 500
  30 /m.php?pbid=open 500
  30 /wc.php 500
  30 /xshell.php 500
  30 /xw1.php 500
  30 /yao.php 500
  30 /yumo.php 500
  31 /12.php 500
  31 /1213.php 500
  31 /3.php 500
  31 /56.php 500
  31 /9678.php 500
  31 /ak.php 500
  31 /ak47.php 500
  31 /ak48.php 500
  31 /aotu.php 500
  31 /bak.php 500
  31 /cainiao.php 500
  31 /cmd.php 500
  31 /conflg.php 500
  31 /data.php 500
  31 /db__.init.php 500
  31 /db_dataml.php 500
  31 /db_desql.php 500
  31 /defect.php 500
  31 /fack.php 500
  31 /feixiang.php 500
  31 /h1.php 500
  31 /hm.php 500
  31 /infoo.php 500
  31 /ip.php 500
  31 /l7.php 500
  31 /l8.php 500
  31 /lindex.php 500
  31 /log.php 500
  31 /min.php 500
  31 /mx.php 500
  31 /mz.php 500
  31 /pe.php 500
  31 /phpStudy.php 500
  31 /phpinfi.php 500
  31 /phpstudy.php 500
  31 /post.php 500
  31 /qwe.php 500
  31 /ssaa.php 500
  31 /system.php 500
  31 /wan.php 500
  31 /wanan.php 500
  31 /webdav/ 500
  31 /webslee.php 500
  31 /weixiao.php 500
  31 /wp-admins.php 500
  31 /wshell.php 500
  31 /xiao.php 500
  31 /xiaoma.php 500
  31 /xiaomae.php 500
  31 /xiaomar.php 500
  31 /zuo.php 500
  31 /zuoshou.php 500
  33 /db.init.php 500
  33 /db_session.init.php 500
  34 /w.php 500
  35 /sheep.php 500
  35 /wuwu11.php 500
  35 /xw.php 500
  41 /js/czjl.js 500
  46 /test.php 500
  52 /qaq.php 500
  55 /s.php 500
  62 /q.php 500
  64 /xx.php 500
 121 /qq.php 500
 892 / 500