[bug] Leave application ui issues fixed (#13740)

* validate to_date in leave application

if to_date is less than from_date show message to user
reset to_date value to ''

* var declaration and semicolon missed

* Updated popup message

erpnext/hr/doctype/leave_application/leave_application.js

@@ -110,6 +110,15 @@ frappe.ui.form.on("Leave Application", {
 
 	calculate_total_days: function(frm) {
 		if(frm.doc.from_date && frm.doc.to_date && frm.doc.employee && frm.doc.leave_type) {
+
+			var from_date = Date.parse(frm.doc.from_date);
+			var to_date = Date.parse(frm.doc.to_date);
+
+			if(to_date < from_date){
+				frappe.msgprint(__("To Date cannot be less than From Date"));
+				frm.set_value('to_date', '');
+				return;
+			}
 				// server call is done to include holidays in leave days calculations
 			return frappe.call({
 				method: 'erpnext.hr.doctype.leave_application.leave_application.get_number_of_leave_days',