fix getPtrString

Assets/SibylSystem/coreWrapper.cs

@@ -1190,6 +1190,7 @@ namespace Percy
             var s = Encoding.UTF8.GetBytes(path);
             var ptrFileName = Marshal.AllocHGlobal(s.Length + 1);
             Marshal.Copy(s, 0, ptrFileName, s.Length);
+            Marshal.WriteByte(ptrFileName, s.Length, 0);
             return ptrFileName;
         }