$getCachedTree = $form->_getCachedTree ?? TRUE;
$subType = $form->_subType;
- if (!is_array($subType) && strstr($subType, CRM_Core_DAO::VALUE_SEPARATOR)) {
+ if (!is_array($subType) && strstr(($subType ?? ''), CRM_Core_DAO::VALUE_SEPARATOR)) {
$subType = str_replace(CRM_Core_DAO::VALUE_SEPARATOR, ',', trim($subType, CRM_Core_DAO::VALUE_SEPARATOR));
}