diff --git a/src/DotRecast.Recast.DemoTool/Tools/TileToolImpl.cs b/src/DotRecast.Recast.DemoTool/Tools/TileToolImpl.cs
index 3cc1f7b..8918552 100644
--- a/src/DotRecast.Recast.DemoTool/Tools/TileToolImpl.cs
+++ b/src/DotRecast.Recast.DemoTool/Tools/TileToolImpl.cs
@@ -26,6 +26,9 @@ namespace DotRecast.Recast.DemoTool.Tools
             var settings = _sample.GetSettings();
             var geom = _sample.GetInputGeom();
             var navMesh = _sample.GetNavMesh();
+
+            if (null == settings || null == geom || navMesh == null)
+                return;
             
             float ts = settings.tileSize * settings.cellSize;
             
@@ -44,6 +47,9 @@ namespace DotRecast.Recast.DemoTool.Tools
             var geom = _sample.GetInputGeom();
             var navMesh = _sample.GetNavMesh();
             
+            if (null == settings || null == geom || navMesh == null)
+                return;
+            
             float ts = settings.tileSize * settings.cellSize;
             
             var bmin = geom.GetMeshBoundsMin();