When no effective relief can be granted, an appeal is moot and will be dismissed. (Eye Dog Foundation v. State Board of Guide Dogs for the Blind (1967) 67 Cal. 2d 536, 541 63 Cal. Rptr. 21, 432 P.2d 717.) "The duty of this court . . . is to decide actual controversies by a judgment which can be carried into effect, and not to give opinions upon moot questions or abstract propositions, or to declare principles or rules of law which cannot affect the matter in issue in the case before it." ' . . . 'When, pending an appeal from the judgment of a lower court, and without any fault of the respondent, an event occurs which renders it impossible for this court, if it should decide the case in favor of appellant, to grant him or her any effectual relief whatever, the court will not proceed to a formal judgment, but will dismiss the appeal." (Ibid.)