fix: type casting

[michalsn]

Description
This PR fixes #25

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[michalsn]

Thanks!

[MGatner]

I like the ternary you switched to below.

Suggested change

	if ($hours !== null) {
	$hours = (int) $hours;
	}
	$hours = $hours === null ? null : (int) $hours;