triedb: set default indexer value as zero

Signed-off-by: Delweng <[email protected]>

Author: jsvisa

triedb/pathdb/history_indexer.go

@@ -49,7 +49,10 @@ type indexMetadata struct {
 func loadIndexMetadata(db ethdb.KeyValueReader) *indexMetadata {
 	blob := rawdb.ReadStateHistoryIndexMetadata(db)
 	if len(blob) == 0 {
-		return nil
+		return &indexMetadata{
+			Version: stateIndexVersion,
+			Last:    0,
+		}
 	}
 	var m indexMetadata
 	if err := rlp.DecodeBytes(blob, &m); err != nil {