Update leave_application.js
diff --git a/erpnext/hr/doctype/leave_application/leave_application.js b/erpnext/hr/doctype/leave_application/leave_application.js
index 9413120..4001a45 100755
--- a/erpnext/hr/doctype/leave_application/leave_application.js
+++ b/erpnext/hr/doctype/leave_application/leave_application.js
@@ -41,7 +41,7 @@
 		if (frm.doc.from_date == frm.doc.to_date && frm.doc.half_day == 1){
 			frm.doc.half_day_date = frm.doc.from_date;
 		}else if (frm.doc.half_day == 0){
-			frm.doc.half_day_date = undefined;
+			frm.doc.half_day_date = "";
 		}
 		frm.toggle_reqd("half_day_date", frm.doc.half_day == 1);
 	},