Fix terrain material leak, this should in theory allow the terrain to free its temporary resources

apps/openmw/mwrender/terrainmaterial.cpp

@@ -54,9 +54,10 @@ namespace MWRender
 
     TerrainMaterial::Profile::~Profile()
     {
+        if (mMaterial)
+            sh::Factory::getInstance().destroyMaterialInstance(mMaterial->getName());
     }
 
-
     Ogre::MaterialPtr TerrainMaterial::Profile::generate(const Ogre::Terrain* terrain)
     {
         const Ogre::String& matName = terrain->getMaterialName();