removeMesh bug. _meshes not delete.

src/Layer/babylon.highlightlayer.ts

@@ -826,7 +826,7 @@
                 }
             }
 
-            this._meshes[mesh.uniqueId] = null;
+            delete this._meshes[mesh.uniqueId];
 
             this._shouldRender = false;
             for (var meshHighlightToCheck in this._meshes) {
@@ -951,4 +951,4 @@
             this.onSizeChangedObservable.clear();
         }
     }
-} 
+}