ShapeChecker.IsQuadrilateral System.ArgumentOutOfRangeException

[OrgesKreka]

I am using AForge to detect rectangles on image and the method shapeChecker.IsQuadrilateral throws System.ArgumentOutOfRangeException.
I tracked the execution and it looks like the exception happens in method FindQuadrilateralCorners of class PointsCloud.
Specifically at this part of the code:

// sort other points in counter clockwise order
            float k1 = ( corners[1].X != corners[0].X ) ?
                ( (float) ( corners[1].Y - corners[0].Y ) / ( corners[1].X - corners[0].X ) ) :
                ( ( corners[1].Y > corners[0].Y ) ? float.PositiveInfinity : float.NegativeInfinity );

            float k2 = ( corners[2].X != corners[0].X ) ?
                ( (float) ( corners[2].Y - corners[0].Y ) / ( corners[2].X - corners[0].X ) ) :
                ( ( corners[2].Y > corners[0].Y ) ? float.PositiveInfinity : float.NegativeInfinity );

where it looks like the corners array has only two elements.
As in photo: