Avoid panicking when edit agent emits an empty old_text tag (#30030)

Release Notes:

- Fixed a panic that could sometimes occur when the agent applies edits.

Co-authored-by: Nathan <nathan@zed.dev>
c92b2e31e1Antonio Scandurra committed on 5/6/2025, 6:20:10 PM· committed by GitHubparent09d3ff9
1 file changedLine totals unavailable