pahole: Initialize var to silence -Werror=maybe-uninitialized on gcc version 4.8.5 20150623

That str variable _will_ be initialized at that point, but lets set it
to NULL to silence gcc version 4.8.5 20150623.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
1 file changed