assistant edit tool: Create file when search/replace is empty (#27009)

We used to fail when this happened, but we saw the model use it as a way
to create empty files, which makes sense.

Release Notes:

- N/A
48fe134408Agus Zubiaga committed on 3/18/2025, 6:35:11 PM· committed by GitHubparent22b8662
1 file changedLine totals unavailable