fix: Overallocation of 'qty' from Cr Notes to Parent Invoice

Cr Notes 'qty' are overallocated to parent invoice, when there are
mulitple instances of same item in Invoice.

erpnext/accounts/report/gross_profit/gross_profit.py

@@ -501,7 +501,14 @@ def get_average_rate_based_on_group_by(self):
 						):
 							returned_item_rows = self.returned_invoices[row.parent][row.item_code]
 							for returned_item_row in returned_item_rows:
-								row.qty += flt(returned_item_row.qty)
+								# returned_items 'qty' should be stateful
+								if returned_item_row.qty != 0:
+									if row.qty >= abs(returned_item_row.qty):
+										row.qty += returned_item_row.qty
+										returned_item_row.qty = 0
+									else:
+										row.qty = 0
+										returned_item_row.qty += row.qty
 								row.base_amount += flt(returned_item_row.base_amount, self.currency_precision)
 							row.buying_amount = flt(flt(row.qty) * flt(row.buying_rate), self.currency_precision)
 						if flt(row.qty) or row.base_amount: