use backspace to delete word in interactive-mode will panic

[Sherlock-Holo]

Describe the bug

~/git/mistral.rs/target/release/mistralrs-server -i gguf -m . -f /var/lib/ollama/blobs/sha256-6e9f90f02bb3b39b59e81916e8cfce9deb45aeaeb9a54a5be4414486b907dc1e

use this to start a interactive mode, then

1. input some chinese words, like 你是谁, and we can see the cursor position is correct

2. press backspace to delete one word, we can see the position looks like incorrect

3. press enter, it should only give the words 你是 to the mistral.rs, however, it panic

it seems the interactive mode can't handle the backspace with non-ASCII char

Latest commit or version

87a7c23

[EricLBuehler]

@Sherlock-Holo fixed in #1306.