Possible NULL pointer dereference in hol_entry_help

[Andrei Borzenkov]

Found by Coverity scan for GRUB.

hol_entry_help dereferences state parameter without checking for NULL:

            if (first_long_opt || uparams.dup_args)
              arg (real, "=%s", "[=%s]", state->root_argp->argp_domain,
                   stream);

It is called in several places where "state" is explicitly checked for
being NULL before calling hol_entry_help.