tdb2: make tdb1_null static.

It's only used in two files, make it static in one and do it manually
in the other.

ccan/tdb2/tdb1.h

@@ -42,6 +42,4 @@ uint64_t tdb1_incompatible_hash(const void *key, size_t len, uint64_t seed, void
 
 /* @} ******************************************************************/
 
-extern TDB_DATA tdb1_null;
-
 #endif /* tdb1.h */

ccan/tdb2/tdb1_tdb.c

@@ -28,8 +28,6 @@
 #include "tdb1_private.h"
 #include <assert.h>
 
-TDB_DATA tdb1_null;
-
 /*
   non-blocking increment of the tdb sequence number if the tdb has been opened using
   the TDB_SEQNUM flag
@@ -191,8 +189,11 @@ static TDB_DATA _tdb1_fetch(struct tdb_context *tdb, TDB_DATA key)
 
 	/* find which hash bucket it is in */
 	hash = tdb_hash(tdb, key.dptr, key.dsize);
-	if (!(rec_ptr = tdb1_find_lock_hash(tdb,key,hash,F_RDLCK,&rec)))
-		return tdb1_null;
+	if (!(rec_ptr = tdb1_find_lock_hash(tdb,key,hash,F_RDLCK,&rec))) {
+		ret.dptr = NULL;
+		ret.dsize = 0;
+		return ret;
+	}
 
 	ret.dptr = tdb1_alloc_read(tdb, rec_ptr + sizeof(rec) + rec.key_len,
 				  rec.data_len);

ccan/tdb2/tdb1_traverse.c

@@ -29,6 +29,8 @@
 
 #define TDB1_NEXT_LOCK_ERR ((tdb1_off_t)-1)
 
+static TDB_DATA tdb1_null;
+
 /* Uses traverse lock: 0 = finish, TDB1_NEXT_LOCK_ERR = error,
    other = record offset */
 static tdb1_off_t tdb1_next_lock(struct tdb_context *tdb, struct tdb1_traverse_lock *tlock,