remove exisiting results.

Pathfinding/Pathfinder.cs

@@ -160,6 +160,8 @@ public class Pathfinder
 
     public void SaveResult(string path)
     {
+        if(File.Exists(path))
+            File.Delete(path);
         FileStream fs = new (path, FileMode.CreateNew);
         JsonSerializer.Serialize(fs, pathResult, JsonSerializerOptions.Default);
         fs.Dispose();