A subcontractor as defined in § 43-1, lower-tier subcontractor, or material supplier may not waive or diminish his right to assert payment bond claims or his right to assert claims for demonstrated additional costs in a contract in advance of furnishing any labor, services, or materials. A provision that waives or diminishes a subcontractor’s, lower-tier subcontractor’s, or material supplier’s right to assert payment bond claims or his right to assert claims for demonstrated additional costs in a contract executed prior to providing any labor, services, or materials is null and void.