You may have to written code that checks if an object is null before you use it. For example:

Rexx.Lexer.RexxCodeStatementList list = null;
string name;
if (list != null)
{
   if (list.Count > 1) name =list[1].Name;
}
else
{
   name = "-NA-";
}

This can be abbreviated into the following code using the && operator:

Rexx.Lexer.RexxCodeStatementList list = null;
string name;
if (list != null && list.Count > 1)
{
   name =list[1].Name;
}
else
{
   name = "-NA-";
}

The && (andalso in VB.NET) shortcircuit the if statment when false.