fix: useless validation message (#28029) (#28046)

Co-authored-by: Rucha Mahabal <ruchamahabal2@gmail.com>
(cherry picked from commit 152f9b0a432361f1c801364d1c85c42a16691a8a)

Co-authored-by: Devin Slauenwhite <devin.slauenwhite@gmail.com>
diff --git a/erpnext/payroll/doctype/salary_slip/salary_slip.py b/erpnext/payroll/doctype/salary_slip/salary_slip.py
index 3bc709e..bee96b6 100644
--- a/erpnext/payroll/doctype/salary_slip/salary_slip.py
+++ b/erpnext/payroll/doctype/salary_slip/salary_slip.py
@@ -172,7 +172,6 @@
 						and employee = %s and name != %s {0}""".format(cond),
 						(self.start_date, self.end_date, self.employee, self.name))
 			if ret_exist:
-				self.employee = ''
 				frappe.throw(_("Salary Slip of employee {0} already created for this period").format(self.employee))
 		else:
 			for data in self.timesheets: