fixed typo in MultiTerrainLodControl causing terrains not to be removed

git-svn-id: https://jmonkeyengine.googlecode.com/svn/trunk@10425 75d07b2b-3a1a-0410-a2c5-0572b91ccdca

engine/src/terrain/com/jme3/terrain/geomipmap/MultiTerrainLodControl.java

@@ -80,7 +80,7 @@ public class MultiTerrainLodControl extends TerrainLodControl {
      * the render thread.
      */
     public void removeTerrain(TerrainQuad tq) {
-        removedTerrains.remove(tq);
+        removedTerrains.add(tq);
     }
     
     @Override