filepicker: panic on rename/delete of file that is in filepicker list

**Describe the bug**
If you rename or delete file that is listed with filepicker module it will panic and there is no way to handle it correctly.

I am working on MacOS.

I tried to add recover to my View(), but then there is no way to re-render the view and the page will be blank.

```go
func (m model) View() string {
defer func() {
if r := recover(); r != nil {
fmt.Fprintln(os.Stderr, "Caught panic in filepicker.View:", r)
// recreate filepicker
m.setupFilePicker()
// TODO how to force tea to redraw the view after panic?
}
}()

// ....
```

**To Reproduce**
Steps to reproduce the behavior:
1. create file `test.txt` in home
2. run `examples/file-picker/main.go`, you will see list of files in your home
3. rename or delete file `test.txt` you created with file manager or shell
4. press arrow key down to move in the list
5. the example will panic

**Expected behavior**
It should not crash, or there should be at least possibility to handle this panic in tea view.

Start with examples/file-picker/main.go and reproduce the panic by renaming or deleting a listed file, then pressing the down arrow. Trace how the filepicker handles the changed list; done means the example no longer panics and the view remains usable after the file is renamed or deleted.

Written by the indexing model from the issue text.