Lingering phantom diff in editor

[maxdeviant]

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• Completed

Describe the bug / provide steps to reproduce it

Reproduction steps at 1105876:

1. Open this file
2. On line 29, press Enter twice to produce a diff consisting of two empty lines
3. Click in the gutter to expand the hunk
   
4. Click the "Discard Hunk" button
5. Press Cmd + Z to undo the revert
6. Observe that the diff is back, but only one of the lines is highlighted:
   
7. Click in the gutter to expand the hunk again
8. Click the "Discard Hunk" button
9. 💥 There is now a phantom diff line

Environment

Zed: v0.156.0 (Zed Nightly 6167688)
OS: macOS 14.4.0
Memory: 128 GiB
Architecture: aarch64

If applicable, add mockups / screenshots to help explain present your vision of the feature

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If applicable, attach your Zed.log file to this issue.

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