JSON literals are passed as nil values

[paulourio]

For a statement like SELECT JSON '1' we have the following AST:

QueryStatement [0-15]
  Query [0-15]
    Select [0-15]
      SelectList [7-15]
        SelectColumn [7-15]
          JSONLiteral('1') [7-15]

However, from inside of the n *ast.SelectColumNode, n.Child(0) returns nil instead of a ast.Node with *ast.JSONLiteralNode.

The language feature zetasql.FeatureJsonType is enabled, and other features like FeatureJsonArrayFunctions, FeatureJsonLegacyParse, FeatureJsonNoValidation, FeatureJsonValueExtractionFunctions have no effect.