(a) An agreement modifying a lease contract needs no consideration to be binding.
(b) A signed lease agreement that excludes modification or rescission except by a signed writing may not be otherwise modified or rescinded, but, except as between merchants, such a requirement on a form supplied by a merchant must be separately signed by the other party.
(c) Although an attempt at modification or rescission does not satisfy the requirements of Subsection (b), it may operate as a waiver.
(d) A party who has made a waiver affecting an executory portion of a lease contract may retract the waiver by reasonable notification received by the other party that strict performance will be required of any term waived, unless a retraction would be unjust in view of a material change of position in reliance on the waiver.