open a new editor and quit causes panic / index out of bounds

[erf]

Recreate:

cargo run
q

Crashes with the following message:

panicked at src/editor.rs:223:23:
index out of bounds: the len is 2212 but the index is 2212

it also leaves my terminal in a weird state where i can't select text

version: d1b337c
os: macOS