Whether, under United States v. Munsingwear, a court of appeals' decision should be vacated when an appeal becomes moot by happenstance while a petition for rehearing is pending

Whether, under United States v. Munsingwear, Inc., 340 U.S. 36 (1950), a court of appeals’ decision should be vacated because the appeal became moot by happenstance while a petition for rehearing was pending, as the D.C., Fourth, Eighth, and Eleventh Cir-cuits hold, or instead can be left in place because further review is discretionary, as the Second, Third, Ninth, and Tenth Circuits hold.