As seen in commit cc47c8fa7 (Roland C. Dowdeswell <elric@imrryr.org>,
"Turn on -Wextra -Wno-sign-compare -Wno-unused-paramter and fix
issues"), compilers can be persuaded to dislike a single {NULL} and
prefer {NULL, NULL, NULL, NULL}. That patch altered the C code
directly; here we change the generating file to match.
Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>