Fix english ui-libraries.md

en/manual/ui/ui-libraries.md

@@ -50,7 +50,7 @@ public Button CreateButton()
     if (button != null)
     {        
         // attach a delegate to the Click event
-        someButton.Click += delegate
+        button.Click += delegate
         {
             // do something here...
         };
@@ -67,4 +67,4 @@ UI pages have only one root element. UI libraries can have multiple root element
 * [UI pages](ui-pages.md)
 * [UI editor](ui-editor.md)
 * [Add a UI to a scene](add-a-ui-to-a-scene.md)
-* [Layout system](layout-system.md)
+* [Layout system](layout-system.md)