Add protection in the method is_plugin.

static/plugin_dbui/src/base.js

@@ -227,6 +227,10 @@ Ext.define('App', {
             return false;
         }
 
+        if (component.plugins === undefined) {
+            return false;
+        }
+
         for (i = 0; i < component.plugins.length; i += 1) {
 
             plugin = component.plugins[i];