* dotScene loader: prevent issue when dotScene file is missing an externals section.

git-svn-id: https://jmonkeyengine.googlecode.com/svn/trunk@9767 75d07b2b-3a1a-0410-a2c5-0572b91ccdca

engine/src/ogre/com/jme3/scene/plugins/ogre/SceneLoader.java

@@ -496,7 +496,7 @@ public class SceneLoader extends DefaultHandler implements AssetLoader {
             // == Run 1st pass over XML file to determine material list ==
             materialList = materialLoader.load(assetManager, folderName, info.openStream());
 
-            if (materialList.isEmpty()) {
+            if (materialList == null || materialList.isEmpty()) {
                 // NOTE: No materials were found by searching the externals section.
                 // Try finding a similarly named material file in the same folder.
                 // (Backward compatibility only!)