* nis/nss_nisplus/nisplus-ethers.c: Add missing null pointer check.

	* nis/nss_nisplus/nisplus-hosts.c: Likewise.
	* nis/nss_nisplus/nisplus-network.c: Likewise.
	* nis/nss_nisplus/nisplus-proto.c: Likewise.
	* nis/nss_nisplus/nisplus-rpc.c: Likewise.
	* nis/nss_nisplus/nisplus-service.c: Likewise.
	* nis/nss_nisplus/nisplus-spwd.c: Likewise.