UnstructuredData does not apply --field option

[ilyaukin]

Steps to reproduce

I have a command which returns UnstucturedData, something like

public function myCommand()
{
    return  new UnstructuredData(['id' => '123',....]);
}

Then I run robo my:command --field=id and I expect that I get exact id as string.

Expected behavior

I expect output 123.

Actual behavior

I see the error

 [error]  The format string cannot be used with the data produced by this command, which was an instance of Consolidation\OutputFormatters\StructuredData\UnstructuredData.  Valid formats are: csv,json,list,null,php,print-r,tsv,var_export,xml,yaml 

If I comment out these lines in FormatterManager.php

        if (!is_string($structuredOutput) && !$this->isValidFormat($formatter, $structuredOutput)) {
            $validFormats = $this->validFormats($structuredOutput);
            throw new InvalidFormatException((string)$format, $structuredOutput, $validFormats);
        }

I see the correct result...

System Configuration

OS: Debian GNU/Linux 12 (bookworm)
PHP 8.3.10
Robo 4.0.6