diff --git a/assets/app.js b/assets/app.js
index 5a6cd2d..cd5ab3c 100644
--- a/assets/app.js
+++ b/assets/app.js
@@ -41,6 +41,7 @@ const getTemplateHtml = template => {
 
 const valueChange = value => {
     const iframehtml = document.getElementById('iframe').contentWindow.document.getElementById(value);
+    if(!iframehtml) return;
     const val = document.getElementById(value).value;
     iframehtml.innerHTML = val
 };