I think this can drop core on error if visit_state.lchild or visit_state.rchild are set to newtop.   Maybe this instead:

```
if (visit_state.lchild != NULL) {
        if (visit_state.lchild == newtop)
                newtop = NULL;
        __wt_page_out(session, &visit_state.lchild);
}
if (visit_state.rchild != NULL) {
        if (visit_state.rchild == newtop)
                newtop = NULL;
        __wt_page_out(session, &visit_state.rchild);
}
if (newtop != NULL)
        __wt_page_out(session, &newtop);
```