Silence warning about uninitialized variable.

* src/get-path.c (read_first_line): Initialize variable to keep the
compiler happy.

There's no way that variable can be uninitialized as long as bufsize
is greater than 1, but of course the compiler can't be sure of that...

• Signed-off-by: Damien Goutte-Gattat <dgouttegattat@incenp.org>