With the help of somebody at the Apple Developer Forums I was able to fix the problem by removing the "/Developer/Platforms/iPhoneOS.platform/DeviceSupport/4.2.1 (8C148)" folder. Xcode then re-added the symbols automatically and the error disappeared. For more information see this thread: https://devforums.apple.com/message/367667#367667
解决方案 »
免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货