fix RootRecord

mutable_tree.go

@@ -759,6 +759,7 @@ func (tree *MutableTree) GetImmutable(version int64) (*ImmutableTree, error) {
 
 	tree.mtx.Lock()
 	defer tree.mtx.Unlock()
+	fmt.Println(rootHash)
 	if len(rootHash) == 0 {
 		tree.versions[version] = true
 		return &ImmutableTree{
@@ -878,6 +879,7 @@ func (tree *MutableTree) SaveVersion() ([]byte, int64, error) {
 		// There can still be orphans, for example if the root is the node being
 		// removed.
 		logger.Debug("SAVE EMPTY TREE %v\n", version)
+		fmt.Println("save empty")
 		if err := tree.ndb.SaveOrphans(version, tree.orphans); err != nil {
 			return nil, 0, err
 		}

nodedb.go

@@ -958,6 +958,9 @@ func (ndb *nodeDB) SaveEmptyRoot(version int64) error {
 
 // RootRecord join a root's hash and nodekey, this joined []byte is save in the entry for that root
 func RootRecord(hash []byte, nodeKey []byte) []byte {
+	if len(hash) == 0 || len(nodeKey) == 0 {
+		return []byte{}
+	}
 	bz := make([]byte, hashSize+nodeKeySize)
 	copy(bz[:32], hash)
 	copy(bz[32:], nodeKey)
@@ -966,7 +969,7 @@ func RootRecord(hash []byte, nodeKey []byte) []byte {
 
 func DecodeRootRecord(rootRecord []byte) (hash []byte, nodeKey []byte) {
 	if len(rootRecord) != hashSize+nodeKeySize {
-		return nil, nil
+		return []byte{}, []byte{}
 	}
 	return rootRecord[:32], rootRecord[32:]