Fixed bug in datagrid tutorial:

The image for the Defender icons in the scoreboard was still pointing to the old PNG (which no longer exists).

Samples/tutorial/datagrid/data/tutorial.rml

@@ -18,7 +18,7 @@
             height: 16px;
 
             defender-decorator: defender;
-            defender-image-src: high_scores_defender.png;
+            defender-image-src: ../../../assets/high_scores_defender.tga;
         }
 	</style>
 </head>