fix image link

docs/modules/tutorials/pages/beginner/hello_material.adoc

@@ -7,7 +7,7 @@
 
 The term Material includes everything that influences what the surface of a 3D model looks like: The color, texture, shininess, and opacity/transparency. Plain coloring is covered in <<jme3/beginner/hello_node#,Hello Node>>. Loading models that come with materials is covered in <<jme3/beginner/hello_asset#,Hello Asset>>. In this tutorial you learn to create and use custom JME3 Material Definitions.
 
-image::jme3/beginner/beginner-materials.png[beginner-materials.png,320,240,align="center"]
+image::beginner/beginner-materials.png[beginner-materials.png,320,240,align="center"]