bug#41700: grep -v always exiting with 1 for empty file

[Andi Kleen]

% grep --version
grep (GNU grep) 3.4
...
% echo -n > foo
% grep -v foo foo ; echo $?
1

Would expect it to exit with zero in this case, since foo is not in the
file.

When the file is one byte it works as expected:

% echo > foo
% grep -v foo foo ; echo $?

0
%