There was a name clash with my new proeprty. Oops\!

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@7318 178a84e3-b1eb-0310-8ba1-8eac791a3b58

src/graphics/material.cpp

@@ -79,7 +79,7 @@ Material::Material(const XMLNode *node, int index)
     else
         m_graphical_effect = GE_NONE;
 
-    node->get("alpha", &s);
+    node->get("compositing", &s);
     if      (s == "blend")    m_alpha_blending = true;
     else if (s == "test")     m_alpha_testing = true;
     else if (s == "additive") m_add = true;