Invalid detection of use after delete

Please consider the following code using libraries:
```
function cleanupTickets(Storage storage self) internal {
delete self.tickets;
self.tail = 0;
}
```

`use-after-delete` detector reports:
> Using values of variables after they have been explicitly deleted may lead to unexpected behavior or compromise
>
> GroupSelection.cleanupTickets(GroupSelection.Storage) uses a variable after it was deleted
> - Delete: delete self.tickets
> - Use: self.tail = 0

I think the detector is wrong, and it's looking only at `self` part of the line. We are deleting `self.tickets` and `self.tail` can be safely used.