Core/Vmaps: Reduce memory used by vmaps (and their size, slightly)

src/common/Collision/Maps/MapTree.cpp

@@ -16,17 +16,18 @@
  */
 
 #include "MapTree.h"
-#include "ModelInstance.h"
-#include "VMapManager2.h"
-#include "VMapDefinitions.h"
-#include "Log.h"
 #include "Errors.h"
+#include "Log.h"
 #include "Metric.h"
+#include "ModelInstance.h"
+#include "VMapDefinitions.h"
+#include "VMapManager2.h"
+#include "WorldModel.h"
 
-#include <string>
-#include <sstream>
 #include <iomanip>
 #include <limits>
+#include <sstream>
+#include <string>
 
 using G3D::Vector3;
 
@@ -349,7 +350,7 @@ namespace VMAP
         {
             iTreeValues[i->first].setUnloaded();
             for (uint32 refCount = 0; refCount < i->second; ++refCount)
-                vm->releaseModelInstance(iTreeValues[i->first].name);
+                vm->releaseModelInstance(iTreeValues[i->first].getWorldModel()->GetName());
         }
         iLoadedSpawns.clear();
         iLoadedTiles.clear();