Do not detach NPC parts in destructor

apps/openmw/mwrender/animation.cpp

@@ -1409,8 +1409,13 @@ namespace MWRender
 
     PartHolder::~PartHolder()
     {
-        if (mNode->getNumParents())
+        if (mNode.get() && mNode->getNumParents())
             mNode->getParent(0)->removeChild(mNode);
     }
 
+    void PartHolder::unlink()
+    {
+        mNode = NULL;
+    }
+
 }

apps/openmw/mwrender/animation.hpp

@@ -55,6 +55,9 @@ public:
 
     ~PartHolder();
 
+    /// Unreferences mNode *without* detaching it from the graph. Only use if you know what you are doing.
+    void unlink();
+
     osg::ref_ptr<osg::Node> getNode()
     {
         return mNode;

apps/openmw/mwrender/npcanimation.cpp

@@ -273,6 +273,13 @@ NpcAnimation::~NpcAnimation()
             // all from within this destructor. ouch!
            && mPtr.getRefData().getCustomData() && mPtr.getClass().getInventoryStore(mPtr).getListener() == this)
         mPtr.getClass().getInventoryStore(mPtr).setListener(NULL, mPtr);
+
+    // do not detach (delete) parts yet, this is done so the background thread can handle the deletion
+    for(size_t i = 0;i < ESM::PRT_Count;i++)
+    {
+        if (mObjectParts[i].get())
+            mObjectParts[i]->unlink();
+    }
 }
 
 NpcAnimation::NpcAnimation(const MWWorld::Ptr& ptr, osg::ref_ptr<osg::Group> parentNode, Resource::ResourceSystem* resourceSystem,