View invoice in backend breaks page (layout will not load)

Question

The version of my magento2 is 2.3.5-p1.

Here is the problem: We will open the invoice view in backend. So we go to: ->Sales->orders->select an order ->go to Invoices->view

Does someone has the same issue and were able to fix it? Any ideas how to fix it?

I am happy for any ideas!

Thanks for helping.

Totals.php

public function afterGetTotals(\Magento\Sales\Block\Order\Totals $subject, ?array $totals)
{
    if (!is_array($totals)) {
        return null;
    }
    foreach ($totals as $total) {
        if ($total->getCode() == 'discount') {
            if ($this->_coreRegistry->registry('current_order')->getAppliedRuleIds() == self::POS_CUSTOM_DISCOUNT
                && $this->_coreRegistry->registry('current_order')->getOsPosCustomDiscountAmount()) {
                $label = "Custom Discount";
                if ($this->_coreRegistry->registry('current_order')->getOsPosCustomDiscountType()
                    == self::PERCENT_PRICE_TYPE) {
                    $label .= sprintf(
                        " (%.2f%%)",
                        $this->_coreRegistry->registry('current_order')->getOsPosCustomDiscountAmount()
                    );
                }
                $total->setLabel($label);
            }
        }
    }
    return $totals;
}

Answer 1

This line is checking whether the AppliedRuleIds value of the current order object is equal to self::POS_CUSTOM_DISCOUNT, and whether the OsPosCustomDiscountAmount value of the current order object is not empty.

If the current_order object is null or if the AppliedRuleIds value or OsPosCustomDiscountAmount value are not defined, then the code could result in a fatal error due to a null pointer exception.

To prevent the null pointer exception, you can add null checks to ensure that the current_order object is not null and that the values you are trying to access are defined before accessing them.

Use this code on line 29,

$currentOrder = $this->_coreRegistry->registry('current_order');
if ($currentOrder && $currentOrder->getAppliedRuleIds() == self::POS_CUSTOM_DISCOUNT
                && $currentOrder->getOsPosCustomDiscountAmount()) {