Make nullable parameter types explicit to avoid deprecation warnings

[zigzagdev]

What’s been done

Just a quick tidy-up.
PHP 8.1 started warning about implicitly nullable parameters, and PHP 8.4 is going to make them a hard error.
So I’ve updated the function signatures to use ?type syntax explicitly.

Before:

public function example(string $name = null)

After:

 public function example(?string $name = null)

This keeps us ahead of future PHP upgrades and makes the intent a bit clearer.
Shouldn’t affect any actual logic — purely a syntax-level fix.

Let me know if anything needs tweaking!

[freekmurze]

Thanks!