diff --git a/static/js/components/app-main/index.js b/static/js/components/app-main/index.js
index e6b7f19..8b22f76 100644
--- a/static/js/components/app-main/index.js
+++ b/static/js/components/app-main/index.js
@@ -56,7 +56,7 @@ function createXTerm(name, xtermNode){
   var xterm;
   var runtime = window.AppRuntime[name];
 
-  if (Terminal.focus) {
+  if (Terminal.focus && Terminal.focus.screen) {
     xtermNode.removeChild(Terminal.focus.screen);
   }
 
diff --git a/static/js/components/app-main/worker.js b/static/js/components/app-main/worker.js
deleted file mode 100644
index f8678b9..0000000
--- a/static/js/components/app-main/worker.js
+++ /dev/null
@@ -1,5 +0,0 @@
-/**
- * Created by nuintun on 2015/11/27.
- */
-
-importScripts();