[REF] Fix Page Hook test on php8 by putting in guard into customDataB…

[seamuslee001]

…lock around the SubType variable

Overview

CRM_Core_Page_HookTest fails on php8 due to an e-notice

Before

Test fails

CRM_Core_Page_HookTest::testFormsCallBuildFormOnce
Undefined array key "customDataSubType"

/home/jenkins/bknix-edge/build/build-0/web/sites/default/files/civicrm/templates_c/en_US/%%9F/9F8/9F828591%%customDataBlock.tpl.php:18
/home/jenkins/bknix-edge/build/build-0/web/sites/all/modules/civicrm/packages/Smarty/Smarty.class.php:1914
/home/jenkins/bknix-edge/build/build-0/web/sites/default/files/civicrm/templates_c/en_US/%%4C/4C5/4C5F7411%%EntityForm.tpl.php:36
/home/jenkins/bknix-edge/build/build-0/web/sites/all/modules/civicrm/packages/Smarty/Smarty.class.php:1914
/home/jenkins/bknix-edge/build/build-0/web/sites/default/files/civicrm/templates_c/en_US/%%7A/7AF/7AF88B87%%RelationshipType.tpl.php:6

After

Test passes on php8

ping @eileenmcnaughton @demeritcowboy

[civibot]

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