Execption when `Delimiter` is initialized from other string variable and not a string litteral

[hlovdal]

Describe the bug

When CsvConfiguration.Delimiter is initialized with ";" things work, but if it is initialized from a variable like public static string Delimiter { get; set; } = ";"; then the program crashes later on.

To Reproduce

    internal class CsvManager
    {
        public static string Delimiter { get; set; } = ";";

        private static CsvConfiguration GetCsvConfiguration()
        {
            var config = new CsvConfiguration(CultureInfo.InvariantCulture)
            {
                // Delimiter = Delimiter  // exception
                Delimiter = ";"  // works
            };
            return config;
        }

        public static List<SomeData> ReadData(string path)
        {
            using var reader = new StreamReader(path);
            using var csv = new CsvReader(reader, GetCsvConfiguration());
            return csv.GetRecords<SomeData>().ToList();
        }

        public static void WriteData(string path, IEnumerable<SomeData> data)
        {
            using var writer = new StreamWriter(path);
            using var csv = new CsvWriter(writer, GetCsvConfiguration());
            csv.WriteRecords(data);
        }
    }

When calling WriteData and having Delimiter = Delimiter active the program crashes with the following stacktrace:

Unhandled exception. System.ArgumentNullException: Value cannot be null. (Parameter 'source')
   at System.Linq.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument)
   at System.Linq.Enumerable.SelectMany[TSource,TResult](IEnumerable`1 source, Func`2 selector)
   at CsvHelper.CsvWriter..ctor(TextWriter writer, IWriterConfiguration configuration, Boolean leaveOpen)
   at ....CsvManager.WriteData(String path, IEnumerable`1 data) in ...\CsvManager.cs:line 35

Same behaviour on versions 27.2.1 and 30.0.1.