- fix possible NPE in BulletAppState

git-svn-id: https://jmonkeyengine.googlecode.com/svn/trunk@10344 75d07b2b-3a1a-0410-a2c5-0572b91ccdca

engine/src/bullet-common/com/jme3/bullet/BulletAppState.java

@@ -212,15 +212,17 @@ public class BulletAppState implements AppState, PhysicsTickListener {
     }
 
     public void update(float tpf) {
-        if (debugEnabled && debugAppState == null) {
+        if (debugEnabled && debugAppState == null && pSpace != null) {
             debugAppState = new BulletDebugAppState(pSpace);
             stateManager.attach(debugAppState);
             pSpace.enableDebug(app.getAssetManager());
         } else if (!debugEnabled && debugAppState != null) {
             stateManager.detach(debugAppState);
             debugAppState = null;
+            if (pSpace != null) {
                 pSpace.enableDebug(null);
             }
+        }
         //TODO: remove when deprecation of PhysicsSpace.enableDebug is through
         if (pSpace.getDebugManager() != null && !debugEnabled) {
             debugEnabled = true;