How to handle null values with JSON function in SQL statements: Function json(unknown) does not exist

Is it possible to avoid issues with null values from dynamic parameters when using the JSON function in SQL queries? The problem is that if a null value is given to a query (See example below as a rough, untested example), an error occurs Npgsql.PostgresException: "42883: Function json(unknown) does not exist

The following code is an example. The parameter areAttributesNull and the string replace is added to avoid the issue, but this is not really a desired (and practicable) solution. Maybe, there is already a more simple way to handle the data properly without the need to string-replace SQL statements, but I didn't find any other solution yet...

using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Dapper;
					
public class Program
{
    public async Task<int> UpdateNodes(List<Node> nodes, bool areAttributesNull = false)
    {
        if (nodes is null || nodes.Count == 0)
            return 0;
        // Not relevant, get a connection to the database somehow.
        await using var connection =  await this.GetDatabaseConnection();

        var sqlParams = nodes.Select(node => new DynamicParameters(new
        {
            id = node.Id,
            description = node.Description,
            jsonattributes = node.JsonAttributes
        }));

        var sql = @"UPDATE node SET (id, description, jsonattributes) = 
            (@id, @description, JSON(@jsonattributes)) WHERE id = @id;";
		
        if (areAttributesNull)
        {
            sql = sql.Replace(", jsonattributes", "");
            sql = sql.Replace(", JSON(@jsonattributes)", "");
        }

        return await connection.ExecuteAsync(sql, sqlParams);
    }

    public async Task<NpgsqlConnection> GetDatabaseConnection()
    {
        var connection = new NpgsqlConnection("SomeConnectionString");
        await connection.NpgsqlConnection.OpenAsync();
        return connection;
    }
}

public class Node
{
    public string Id { get; set; }
	
    public string Description { get; set; }
	
    public string? JsonAttributes { get; set; }
}

EDIT: For reference, this is no database issue. E.g. SELECT JSON(null), * FROM node; would work properly. Must be something with the mapping.

No repository file or test is named. Start by reproducing the C# UpdateNodes example with a null jsonattributes parameter and the SQL JSON(@jsonattributes) expression, then trace how Dapper maps that parameter. Done means the null case has defined behavior without string replacement and is covered by a regression test.