We explicitly check for and handle the case that the
incoming "path" variable is NULL, but before doing so we
call strchrnul on it, leading to a potential segfault.
We can fix this simply by moving the strchrnul call down; as
a bonus, we can tighten the scope on the associated
variable.
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>