Fix using deadcode and possible use of NULL pointer

Fix for deadcode in unique_create() so that "opened_name" parameter is
always initialized to a valid string or NULL when returning from
function.

Fix for redirect_output() so that "logfile" is not blindly used in
fprintf() call and checked if it is not NULL.

Signed-off-by: Tomas Hozza <thozza@redhat.com>