Fixed memory corrpution (causing a crash when the game ends).

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@8025 178a84e3-b1eb-0310-8ba1-8eac791a3b58

src/items/powerup_manager.cpp

@@ -64,7 +64,7 @@ PowerupManager::~PowerupManager()
             // Note that this test is necessary, since some meshes
             // are also used in attachment_manager!!!
             if(mesh->getReferenceCount()==1)
-                m_all_meshes[(PowerupType)i]->drop();
+                irr_driver->removeMesh(mesh);
         }
     }
 }   // ~PowerupManager