Fix range select -> stage failure when deleted file is already staged

[brandondong]

• PR Description

Fix range select -> stage failure when deleted file is already staged.

Fixes https://github.com/jesseduffield/lazygit/issues/3603

• Please check if the PR fulfills these requirements

• [ ] Cheatsheets are up-to-date (run go generate ./...)
• [x] Code has been formatted (see here)
• [x] Tests have been added/updated (see here for the integration test guide)
• [ ] Text is internationalised (see here)
• [ ] Docs have been updated if necessary
• [x] You've read through your own file changes for silly mistakes etc