Optional types and null propagation

Src/AST/Myc.Ast.Evaluator.pas

@@ -413,6 +413,10 @@ var
     scalarValue: TScalar;
 begin
     baseValue := Node.Base.Accept(Self);
+
+    if baseValue.IsVoid then
+        exit(TDataValue.Void);
+
     indexValue := Node.Index.Accept(Self);
 
     if (indexValue.Kind <> vkScalar) or (indexValue.AsScalar.Kind <> TScalar.TKind.Ordinal) then
@@ -461,6 +465,9 @@ var
 begin
     baseValue := Node.Base.Accept(Self);
 
+    if baseValue.IsVoid then
+        exit(TDataValue.Void);
+
     case baseValue.Kind of
         vkRecordSeries: Result := TDataValue.FromSeries(baseValue.AsRecordSeries.Fields[Node.Member.Value]);
         vkScalarRecord: Result := TDataValue(baseValue.AsScalarRecord.Fields[Node.Member.Value]);