Fix panic when deleting just-generated text (#10282)
Thorsten Ball
and
Conrad
created
We ran into a panic when deleting text that was just generated by a code
action.
This fixes it by ensuring we don't run into a 0-minus-1 panic when a
buffer_range is empty.
Release Notes:
- Fixed panic that could occur when deleting generated-by-unsaved text.
Co-authored-by: Conrad <conrad@zed.dev>