alacritty: Index out of bounds (scroll-back)

Hey 👋,

I noted today when running jest (a JavaScript test runner) that alacritty crashed consistently. This is only happening when running it jest with the --watch option and scrolling.

Reproduce the following way:

• Run jest --watch in a project with a couple of failing tests.
• Scroll up to, lets say, the first failing test.
• Modify and save a watched file, triggering a rerun of jest and resulting in alacritty crashing (output available below with RUST_BACKTRACE=full).

System

OS: Arch Linux Version: alacritty 0.4.0 output Linux/BSD: X11, i3wm only

Logs

Crashes:

thread 'main' panicked at 'index out of bounds: the len is 34 but the index is 39', /build/rust/src/rustc-1.39.0-src/src/libcore/slice/mod.rs:2717:10
stack backtrace:
   0:     0x55954082ad6c - <unknown>
   1:     0x5595406eac8c - <unknown>
   2:     0x55954082a446 - <unknown>
   3:     0x55954082a060 - <unknown>
   4:     0x5595408297af - <unknown>
   5:     0x5595408292df - <unknown>
   6:     0x55954083dfb6 - <unknown>
   7:     0x5595406e4ec9 - <unknown>
   8:     0x5595406e49e4 - <unknown>
   9:     0x55954062f959 - <unknown>
  10:     0x5595404f3f9c - <unknown>
  11:     0x559540579e77 - <unknown>
  12:     0x5595405d9fad - <unknown>
  13:     0x5595405360dd - <unknown>
  14:     0x559540636de3 - <unknown>
  15:     0x55954052cf2e - <unknown>
  16:     0x7f2628649153 - __libc_start_main
  17:     0x5595404b40de - <unknown>
  18:                0x0 - <unknown>

Font/Terminal size:

[2019-12-19 21:46] [INFO] Welcome to Alacritty
[2019-12-19 21:46] [INFO] Configuration loaded from "/home/sqve/.config/alacritty/alacritty.yml"
[2019-12-19 21:46] [DEBUG] Estimated DPR: 2
[2019-12-19 21:46] [DEBUG] Estimated Cell Size: 12 x 30
[2019-12-19 21:46] [DEBUG] Estimated Dimensions: None
[2019-12-19 21:46] [INFO] Device pixel ratio: 2
[2019-12-19 21:46] [INFO] Initializing glyph cache...
[2019-12-19 21:46] [INFO] ... finished initializing glyph cache in 0.017487031s
[2019-12-19 21:46] [INFO] Cell Size: 12 x 30
[2019-12-19 21:46] [INFO] Padding: 8 x 8
[2019-12-19 21:46] [INFO] Width: 1600, Height: 1200
[2019-12-19 21:46] [INFO] PTY Dimensions: Line(39) x Column(132)
[2019-12-19 21:46] [INFO] Initialisation complete
[2019-12-19 21:46] [DEBUG] New num_cols is 98 and num_lines is 69
[2019-12-19 21:46] [INFO] Width: 1192, Height: 2092

🙏