Fixing null issues and ignoring Smarty errors in PHP 8+

[cgsmith]

PHP 8 changes undefined notices to warnings. This causes Smarty 2 to complain a lot and make a very verbose log. This PR mainly address that issues along with the other changes I documented in the CHANGELOG.

Here is a list of the changes as well (note this is all found in the changelog)

Added

• Error handler to LegacySmartyEngine for ignoring PHP 8+ warnings for the frontend
• Links to CHANGELOG for 6.14.2-6.14.3 and unreleased

Fixed

• UserComponent::changeUserWithoutRedirect() undefined oxuser__oxusername
• AdminListController::_setListNavigationParams() actpage default to 0
• SystemInfoController::render() shop key null coalesce check
• ThemeConfiguration::render() null coalesce check
• ArticleListController::getTemplateName() null coalesce check
• ForgotPasswordController::isExpiredLink() expired default to null
• PaymentController::getCheckedPaymentId() isset check for $sCheckedId and null coalesce check on $_SERVER vars
• ThankYouController::getOrder() null check
• Article::updateSoldAmount default $rs to false
• Basket::getPriceForPayment() isset check on oxdelivery
• NewsSubscribed::getOptInStatus null coalesce on oxid oxboptin value
• Order::finalizeOrder() null checks on order number and oxremark
• Order::_updateNoticeList() null check
• Order::getPaymentType() isset check on order
• OrderArticle::getPersParams() isset check
• Payment::delete() is_string and isset check on EOF
• User::getNewsSubscription() isset and null coalescence on news subscriptions
• InputValidator::checkLogin() isset check
• BaseModel::getLanguage() isset check on property
• UtilsUrl::stringToParamsArray() isset check after explode()
• UtilsView::filterTemplateBlocks() null coalesce array variables
• ShopConfiguration::_arrayToMultiline() fix implode error with multidimensional array
• ShopList::render() updatenav check in _aViewData

Removed

• function.oxinputhelp.php unused $blAdmin parameter (no backward compat break - not used)