Signs still sometimes visible after being unplaced

While in an Unstack tab with signs, execute the following:

```
:tab sp
:tabprev
:tabclose
```

The tab that was split still shows a sign in it. Calling `refresh!` does not seem to fix this. The  only way I've been able to make the sign stop appearing is by switching tabs again (but switching tabs within the function/autocmd does not work).
