Error in ParseTree project under Visual Studio 2019

[ekleiman22]

When I run ParseTree project I get error in DrawTree method of LithiumControl.cs in the following row:
p = new Point(graphAbstract.Root.X, graphAbstract.Root.Y);
because graphAbstract.Root == null. I get the following error message:
< System.NullReferenceException: 'Object reference not set to an instance of an object.'
Netron.Lithium.GraphAbstract.Root.get returned null.>
It is not happened when I run the project under Visual Studio 2015

[Alex]

I dig a bit of digging; there was an issue in the initialization of the ParseTree (see fix)
I don't understand why we did not have this exception in the previous versions of Visual Studio.