Fix cleanup issue

apps/openmw/mwworld/cellpreloader.cpp

@@ -169,6 +169,13 @@ namespace MWWorld
     {
     }
 
+    CellPreloader::~CellPreloader()
+    {
+        for (PreloadMap::iterator it = mPreloadCells.begin(); it != mPreloadCells.end();++it)
+            it->second.mWorkItem->waitTillDone();
+        mPreloadCells.clear();
+    }
+
     void CellPreloader::preload(CellStore *cell, double timestamp)
     {
         if (!mWorkQueue)

apps/openmw/mwworld/cellpreloader.hpp

@@ -24,6 +24,7 @@ namespace MWWorld
     {
     public:
         CellPreloader(Resource::ResourceSystem* resourceSystem, Resource::BulletShapeManager* bulletShapeManager, Terrain::World* terrain);
+        ~CellPreloader();
 
         /// Ask a background thread to preload rendering meshes and collision shapes for objects in this cell.
         /// @note The cell itself must be in State_Loaded or State_Preloaded.