KinematicRagdollControl now throws a proper exception when the skeleton control is not found on the model.

git-svn-id: https://jmonkeyengine.googlecode.com/svn/trunk@11083 75d07b2b-3a1a-0410-a2c5-0572b91ccdca

engine/src/bullet-common/com/jme3/bullet/control/KinematicRagdollControl.java

@@ -355,6 +355,9 @@ public class KinematicRagdollControl extends AbstractPhysicsControl implements P
         //I remove the skeletonControl and readd it to the spatial to make sure it's after the ragdollControl in the stack
         //Find a proper way to order the controls.
         SkeletonControl sc = model.getControl(SkeletonControl.class);
+        if(sc == null){
+            throw new IllegalArgumentException("The root node of the model should have a SkeletonControl. Make sure the control is there and that it's not on a sub node.");
+        }
         model.removeControl(sc);
         model.addControl(sc);