title: CATransaction completion block never fires
body: <p>How come the completion block for this CATransaction never fires?</p>
  
  <pre><code>[CATransaction begin];
  [CATransaction setCompletionBlock:^{
      // table animation has finished
      NSLog(@"why does this section never execute?");
  }];
  [self.tableView beginUpdates];
  [self.tableView reloadRowsAtIndexPaths:@[[NSIndexPath indexPathForRow:self.currentFeedItems.count inSection:0]] withRowAnimation:UITableViewRowAnimationFade];
  [self.tableView endUpdates];
  [CATransaction commit];
  </code></pre>
  
  <p>The tableview animation works, but the completion block is never executed. The Apple documentation says that the completion block is guaranteed to execute.</p>