PAnics when adding a new line, no syntax highlighting for rust

[Niedzwiedzw]

❯ hx ~/Programming/workon/src/main.rs
thread 'main' panicked at 'Attempt to index past end of Rope: char index 1662, Rope char length 1662', /home/niedzwiedz/.cargo/registry/src/github.com-1ecc6299db9ec823/ropey-1.2.0/src/rope.rs:996:9
note: run with RUST_BACKTRACE=1 environment variable to display a backtrace
that's when I try to add a new line to the end of a file

[Niedzwiedzw]

so it seems like the cursor can go too far when I press "j" to go down