Fix to TerrainGrid: only clone the grid's material to child quad if it doesn't have a material of its own

git-svn-id: https://jmonkeyengine.googlecode.com/svn/trunk@8970 75d07b2b-3a1a-0410-a2c5-0572b91ccdca

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

@@ -147,7 +147,8 @@ public class TerrainGrid extends TerrainQuad {
                             log.log(Level.FINE, "Loaded TerrainQuad {0} from HeightMapGrid", q.getName());
                         } else if (gridTileLoader != null) {
                             q = gridTileLoader.getTerrainQuadAt(quadCell);
-                            q.setMaterial(material.clone());
+                            // only clone the material to the quad if it doesn't have a material of its own
+                            if(q.getMaterial()==null) q.setMaterial(material.clone());
                             log.log(Level.FINE, "Loaded TerrainQuad {0} from TerrainQuadGrid", q.getName());
                         }
                     }