升级环信sdk时，只是用cocoapod升级了下sdk到2.2.9了，结果就报了很多错误

Undefined symbols for architecture x86_64:    "_OBJC_CLASS_$_EMChatImage", referenced from:        objc-class-ref in ChatSendHelper.o       (maybe you meant: _OBJC_CLASS_$_EMChatImageBubbleView)    "_OBJC_CLASS_$_EMChatLocation", referenced from:        objc-class-ref in ChatSendHelper.o       (maybe you meant: _OBJC_CLASS_$_EMChatLocationBubbleView)    "_OBJC_CLASS_$_EMChatText", referenced from:        objc-class-ref in ChatSendHelper.o       (maybe you meant: _OBJC_CLASS_$_EMChatTextBubbleView)    "_OBJC_CLASS_$_EMImageMessageBody", referenced from:        objc-class-ref in ChatSendHelper.o    "_OBJC_CLASS_$_EMLocationMessageBody", referenced from:        objc-class-ref in ChatSendHelper.o    "_OBJC_CLASS_$_EMMessage", referenced from:        objc-class-ref in ChatSendHelper.o    "_OBJC_CLASS_$_EMTextMessageBody", referenced from:        objc-class-ref in ChatSendHelper.o    "_OBJC_CLASS_$_EMVideoMessageBody", referenced from:        objc-class-ref in ChatSendHelper.o    "_OBJC_CLASS_$_EMVoiceMessageBody", referenced from:        objc-class-ref in ChatSendHelper.o    "_OBJC_CLASS_$_EaseMob", referenced from:        objc-class-ref in ChatSendHelper.o        objc-class-ref in ChatListViewController.o        objc-class-ref in AppDelegate+EaseMob.o        objc-class-ref in MessageModelManager.o        objc-class-ref in ChatViewController.o  ld: symbol(s) not found for architecture x86_64  clang: error: linker command failed with exit code 1 (use -v to see invocation)