fix: rate changing while making PR (negative discount) (backport #40539…

…) (#40540)

fix: rate changing while making PR (negative discount) (#40539)

(cherry picked from commit 8136954)

Co-authored-by: rohitwaghchaure <rohitw1991@gmail.com>

erpnext/public/js/controllers/taxes_and_totals.js

@@ -26,7 +26,7 @@ erpnext.taxes_and_totals = class TaxesAndTotals extends erpnext.payments {
 			item.discount_amount = flt(item.rate_with_margin) * flt(item.discount_percentage) / 100;
 		}
 
-		if (item.discount_amount) {
+		if (item.discount_amount > 0) {
 			item_rate = flt((item.rate_with_margin) - (item.discount_amount), precision('rate', item));
 			item.discount_percentage = 100 * flt(item.discount_amount) / flt(item.rate_with_margin);
 		}