The app quits in text mode if I press the backspace when the text cursor is at the very start of canvas grid

[widcardw]

https://user-images.githubusercontent.com/55699713/225813550-b05b699f-1263-4164-bbcc-30fe8268f755.mp4

Also, when the cursor reaches the top edge of canvas, and I press the UpArrow key, the app crashes.

After browsing the source code, I've found that the cursor_position is changed without judging if it is out of usize range.

Environment:

• macOS 13.2.1 Apple Silicon