PHP Deprecated: round(): Passing null to parameter #1 ($num) of type int|float is deprecated in

PHP Deprecated: round(): Passing null to parameter #1 ($num) of type int|float is deprecated in
“PREPAID_TAXABLE_AMOUNT”=> (($item->getDiscountAmount()) ? abs( round($item->getSubTotal(), 2) – round($item->getDiscountAmount(), 2) ) : ” )

I am getting this error in PHP 8 & Magento2.4

How to solve it?