fix: allow to parse null or empty header element

[EnThib]

Why I open this pull request ?

When I pass a empty string value at the first arguments of parseHeader function, it throw an exception :

Argument 1 passed to Smalot\PdfParser\Parser::parseHeader() must be of the type array, string given, called in /path/to/project/vendor/smalot/pdfparser/src/Smalot/PdfParser/Parser.php on line 266

that append when I provide a PDF like this : 20221025_debug_header_parse.pdf

If it helps, I have already opened a case for this problem. : #557

Have a good day ^^

[k00ni]

@DogLoc thank you for this fix. I have a few things:

• Can you move the new if-clause before the switch-clause? I can not see why this check is only relevant for the >> case.
• Please provide at least one test. If you need help here, let me know.
• Please fix failing CS workflow by running PHP-CS-Fixer.
• Out of curiosity: why not return ElementNull instead? Why do you use null?

[EnThib]

@DogLoc thank you for this fix. I have a few things:

• Can you move the new if-clause before the switch-clause? I can not see why this check is only relevant for the >> case.
• Please provide at least one test. If you need help here, let me know.
• Please fix failing CS workflow by running PHP-CS-Fixer.
• Out of curiosity: why not return ElementNull instead? Why do you use null?

Finally I use an empty array for input and output (<<, >>) because with the ElementNull class, the code tries to retrieve the header on a null element I don't have strong knowledge of this project, so if you have a better suggestion, I take it! ^^

I have provided a unit test for the parser, let me know if this is sufficient.

[EnThib]

@k00ni master merged in my branch 👍

[k00ni]

Thank you for your changes! There is only one thing and we are good to go.

[k00ni]

Looks good to me. I will merge it next week if there are no objections.

Thank you @DogLoc!

[EnThib]

Thanks you too ^^ ! @k00ni