Several Arizona citizens brought a diversity suit in a federal district court against Harsh Building Company, an Oregon corporation. All parties involved in the suit stipulated that the defendant had its principal place of business in Oregon. During the trial, evidence showed that the only real business activity of Harsh Building Co. was owning and operating the Phoenix apartment complex, which was the subject of the suit. The plaintiffs lost the suit. On appeal, they claimed that the district court did not have jurisdiction because of lack of diversity of citizenship. Did the plaintiffs waive their right to challenge jurisdiction?