Fixed a IndexOutOfBoundsException when residual weights are present

jme3-blender/src/main/java/com/jme3/scene/plugins/blender/meshes/MeshHelper.java

@@ -291,6 +291,8 @@ public class MeshHelper extends AbstractBlenderHelper {
         	Structure defbase = (Structure) parent.getFieldValue("defbase");
             List<String> groupNames = new ArrayList<String>();
             List<Structure> defs = defbase.evaluateListBase();
+            
+            if(!defs.isEmpty()) {
                 for (Structure def : defs) {
                     groupNames.add(def.getFieldValue("name").toString());
                 }
@@ -315,6 +317,7 @@ public class MeshHelper extends AbstractBlenderHelper {
                     }
                 }
             }
+        }
         return result;
     }