fix posting date in journal entry on load (#12694)

diff --git a/erpnext/accounts/doctype/journal_entry/journal_entry.js b/erpnext/accounts/doctype/journal_entry/journal_entry.js
index 48062a3..60c974f 100644
--- a/erpnext/accounts/doctype/journal_entry/journal_entry.js
+++ b/erpnext/accounts/doctype/journal_entry/journal_entry.js
@@ -82,8 +82,8 @@
 			$.each(this.frm.doc.accounts || [], function(i, jvd) {
 				frappe.model.set_default_values(jvd);
 			});
-
-			if(!this.frm.doc.amended_from) this.frm.doc.posting_date = this.frm.posting_date || frappe.datetime.get_today();
+			var posting_date = this.frm.posting_date;
+			if(!this.frm.doc.amended_from) this.frm.set_value('posting_date', posting_date || frappe.datetime.get_today());
 		}
 	},