Fix error when <BS> at beginning of document (#691)
Fix error when <BS> at beginning of document (#691)


VSCodeVim/Vim,Chillee/Vim,Chillee/VSCodeNeovim,rufusroflpunch/Vim,Chillee/Vim,Chillee/VSCodeNeovim,Chillee/VSCodeNeovim,VSCodeVim/Vim,westim/Vim,rufusroflpunch/Vim,westim/Vim,westim/Vim