lib/db: Remove all sequences related to the folder (fixes #4928) (#4929)

lib/db/leveldb_dbinstance.go

@@ -539,6 +539,14 @@ func (db *Instance) dropFolder(folder []byte) {
 	}
 	dbi.Release()
 
+	// Remove all sequences related to the folder
+	sequenceKey := db.sequenceKey([]byte(folder), 0)
+	dbi = t.NewIterator(util.BytesPrefix(sequenceKey[:4]), nil)
+	for dbi.Next() {
+		db.Delete(dbi.Key(), nil)
+	}
+	dbi.Release()
+
 	// Remove all items related to the given folder from the global bucket
 	dbi = t.NewIterator(util.BytesPrefix([]byte{KeyTypeGlobal}), nil)
 	for dbi.Next() {