If edit->column_highlight is on and the disk is so full that the editor
is unable even to write the magic (r <= 0), then subsequent if (len)
check might fail, since the value of len is undefined.
The solution is to initialize len with a non-zero value, so that the
function properly returns an error value in all cases (adding an
explicit return 0; is also possible, but then one must take care of
closing file descriptors, which is less convenient).
Signed-off-by: Yury V. Zaytsev <yury@shurup.com>
fbc013421c