Fixed link to TestNiftyGui.java.

src/docs/asciidoc/jme3/advanced/nifty_gui_overlay.adoc

@@ -28,7 +28,7 @@ On this page, we look at the overlay variant, which is more commonly used in gam
 == Sample Code
 
 
-*  link:https://github.com/jMonkeyEngine/jmonkeyengine/blob/master/jme3-examples/src/main/java/jme3test/niftygui/TestNiftyGui.java[TestNiftyGui.java]
+*  link:https://github.com/jMonkeyEngine/jmonkeyengine/blob/master/jme3-examples/src/main/java/jme3test/niftygui/TestNiftyGui.java[TestNiftyGui.java]
 
 [TIP]
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