protects [them] from engaging in speculation or wasting their resources through the review of potential or abstract disputes,' Digital Props., Inc." City of Plantation, 121 F.3d 586, 589 (11th Cir.1997)." United States I. Rivera, 613 F.3d 1046, 1050 (11th Cir. 2010); see also Pittman I. Cole, 267 F.3d 1269, 1278 (