Added parent filter to the Salary Structure Employee since it was getting base and variable value from first found Salary Structure Employee (#8756)

diff --git a/erpnext/hr/doctype/salary_slip/salary_slip.py b/erpnext/hr/doctype/salary_slip/salary_slip.py
index e422958..c7bbe65 100644
--- a/erpnext/hr/doctype/salary_slip/salary_slip.py
+++ b/erpnext/hr/doctype/salary_slip/salary_slip.py
@@ -99,7 +99,8 @@
 		'''Returns data for evaluating formula'''
 		data = frappe._dict()
 
-		data.update(frappe.get_doc("Salary Structure Employee", {"employee": self.employee}).as_dict())
+		data.update(frappe.get_doc("Salary Structure Employee",
+			{"employee": self.employee, "parent": self.salary_structure}).as_dict())
 
 		data.update(frappe.get_doc("Employee", self.employee).as_dict())
 		data.update(self.as_dict())