vim.eval("v:char") hangs if {char2} of digraph input is <BS>

[tomtomjhj]

Ultisnips registers an au InsertCharPre * that calls a python function that runs vim.eval("v:char"). With this plugin enabled, pressing <BS> as the second char makes nvim hang. Of course passing <BS> to {char2} doesn't do something interesting, but I frequently do this by mistake.

To reproduce,

1. nvim -u NORC
2. :au InsertCharPre * py3 import vim; vim.eval("v:char")
3. i<C-k>a<BS>

I'm using the latest version of nvim and pynvim.

[tomtomjhj]

closed by #439