minor fix (#15503)

diff --git a/erpnext/selling/sales_common.js b/erpnext/selling/sales_common.js
index b7b186a..c431df4 100644
--- a/erpnext/selling/sales_common.js
+++ b/erpnext/selling/sales_common.js
@@ -264,7 +264,7 @@
 		{
 			row.incentives = flt(
 					row.allocated_amount * row.commission_rate / 100.0,
-					precision("incentives", sales_person));
+					precision("incentives", row));
 		}
 	},