[BUG] Delete character (0x7F) propagates to `inputValue` when deleting a selected item

- `downshift` version: 6.1.7
- `node` version: 14.18.1
- `npm` (or `yarn`) version: yarn 1.22.15

**Description of the bug:**

When the `useMultipleSelection` hook uses a controlled `selectedItems` prop, the delete character (0x7F) gets outputted to the text input after deleting the last selected item.

**Code**:

Here's a code sandbox with the sample code found in the docs but `selectedItems` is used instead of `initialSelectedItems`:

https://codesandbox.io/s/downshift-bug-controlled-multi-selection-dc1u7?file=/src/DropdownMultipleCombobox.js

**Steps to reproduce:**

1. Click on one of the selected items (apple or orange)
2. Press DELETE
3. Press DELETE
4. Delete character (0x7F) should appear inside the text input

https://user-images.githubusercontent.com/1303285/152700531-8eb0316e-f34b-4432-897c-e959dc608acc.mp4