busybox

lineedit: fix SEGV in isk, hexedit, ed, closes 11661

fdisk, hexedit and ed calls read_line_edit in libbb/lineedit.c with NULL
as first argument. On line 2373 of lineedit.c of busybox version 1.29.3,
state->hist_file is referenced without checking the state->flag.

This causes segmentation fault on fdisk, hexedit and ed on ARM Cortex-A9.
It somehow works on x86_64.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>