fix: update fieldname in filter

(cherry picked from commit 99bc02d0e0)

erpnext/selling/doctype/party_specific_item/party_specific_item.py

@@ -23,13 +23,13 @@ class PartySpecificItem(Document):
 
 	def validate(self):
 		exists = frappe.db.exists(
+			"Party Specific Item",
 			{
-				"doctype": "Party Specific Item",
 				"party_type": self.party_type,
 				"party": self.party,
 				"restrict_based_on": self.restrict_based_on,
-				"based_on": self.based_on_value,
-			}
+				"based_on_value": self.based_on_value,
+			},
 		)
 		if exists:
 			frappe.throw(_("This item filter has already been applied for the {0}").format(self.party_type))