Commented Issue: ManhattanShapes error [24146]

I am experiencing a little problem in converting an integer raster to polygon shapefile using manhattanshapes.

here is the code

Dim a As New DotSpatial.Plugins.Taudem.Port.ManhattanShapes(fname)

Dim g As New FeatureSet(FeatureType.Polygon)
g.Filename = TextBox1.Text

g = a.GridToShapeManhattan()

the instructions above works fine, the problem I am encountering is that the create shapefile often has errors such as the one in the attached capture.

Basically gridToShapeManhattan is supposed to create shapefiles with only vertical and horizontal borders, while sometimes I find such errors.
Comments: ** Comment from web user: mogikanin **

if you do not want to use cancelprogresshandler create and pass instance of this class

```
class MockProgressHandler : ICancelProgressHandler
{
public void Progress(string key, int percent, string message)
{
//nothing
}

public bool Cancel { get { return false; } }
}

```
But i'll also check why it not working with null.