环信 消息页面tableview 滚动到最后一行报错

 Assertion failure in -[UITableViewRowData _assertValidIndexPath:allowEmptySection:], /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit_Sim/UIKit-3505.16/UITableViewRowData.m:2310

2015-10-21 15:36:43.454 ttt[6899:1602153] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid indexPath'  
 
每次下拉刷新 都是这个方法崩溃