Absent an express waiver of the contractual provision, the application of the waiver and judicial estoppel doctrines require a showing of prejudice. Thus, waiver "is a voluntary act and implies an abandonment of a right or privilege--an election to dispense with something of value or to forego some advantage which one might, at his option, have demanded or insisted upon. In no case will a waiver be presumed or implied contrary to the intention of the party whose rights would be injuriously affected thereby, unless by his conduct the opposite party has been misled, to his prejudice, into the honest belief that such waiver was intended or consented to." (McDanels v. General Ins. Co. (1934) 1 Cal.App.2d 454, 460 36 P.2d 829.) Rhe dual goals of judicial estoppel " ' "are to maintain the integrity of the judicial system and to protect parties from opponents' unfair strategies." ' " (Aguilar v. Lerner, supra, 32 Cal.4th at p. 986.) Thus, the common theme of these legal doctrines is the prevention of unfairness.