fix: allow zero valuation rate (backport #44902) (#44910)

fix: allow zero valuation rate (#44902)

(cherry picked from commit 614a8f1)

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

erpnext/stock/stock_ledger.py

@@ -937,7 +937,7 @@ def get_serialized_values(self, sle):
 				# else it remains the same as that of previous entry
 				self.wh_data.valuation_rate = new_stock_value / new_stock_qty
 
-		if not self.wh_data.valuation_rate and sle.voucher_detail_no:
+		if self.wh_data.valuation_rate is None and sle.voucher_detail_no:
 			allow_zero_rate = self.check_if_allow_zero_valuation_rate(sle.voucher_type, sle.voucher_detail_no)
 			if not allow_zero_rate:
 				self.wh_data.valuation_rate = self.get_fallback_rate(sle)