[minor] validate email address before get update button click
diff --git a/erpnext/templates/includes/footer/footer_extension.html b/erpnext/templates/includes/footer/footer_extension.html
index 897a804..5d706a4 100644
--- a/erpnext/templates/includes/footer/footer_extension.html
+++ b/erpnext/templates/includes/footer/footer_extension.html
@@ -12,7 +12,7 @@
 frappe.ready(function() {
 	$("#footer-subscribe-button").click(function() {
 
-		if($("#footer-subscribe-email").val()) {
+		if($("#footer-subscribe-email").val() && valid_email($("#footer-subscribe-email").val())) {
 			$("#footer-subscribe-email").attr('disabled', true);
 			$("#footer-subscribe-button").html("Sending...")
 				.attr("disabled", true);
@@ -31,7 +31,7 @@
 			});
 		}
 		else
-			frappe.msgprint(frappe._("Please enter email address"))
+			frappe.msgprint(frappe._("Please enter valid email address"))
 	});
 });
 </script>