Modifying company_tagline function for compatibility with PHP 8.1

[lakellie]

We heard from a user in the forums that there is a deprecated PHP warning for the following code in in wp-job-manager/wp-job-manager-template.php line 1093:

if ( 0 === strlen( $company_tagline ) ) {
		return;
	}

The PHP warning states:

Deprecated: strlen(): Passing null to parameter #1 ($string) of type string, please use ! empty function for this

Thanks!