/bin$ ./lolnerod
2020-10-26 02:40:15.023 I Lolnero 'Hello World' (v0.4.0.0-release)
2020-10-26 02:40:15.023 I Initializing cryptonote protocol...
2020-10-26 02:40:15.024 I Cryptonote protocol initialized OK
2020-10-26 02:40:15.025 I Initializing core...
2020-10-26 02:40:15.025 I Loading blockchain from folder /home/cheng/.lolnero/lmdb ...
2020-10-26 02:40:15.028 W DB error attempting to fetch block index from hashMDB_BAD_TXN: Transaction must abort, has a child, or is invalid
2020-10-26 02:40:15.031 E Exception at [add_new_block], what=DB error attempting to fetch block index from hashMDB_BAD_TXN: Transaction must abort, has a child, or is invalid
2020-10-26 02:40:15.031 E Failed to add genesis block to blockchain
2020-10-26 02:40:15.033 W Failed to commit a transaction to the db: MDB_BAD_TXN: Transaction must abort, has a child, or is invalid
terminate called after throwing an instance of 'cryptonote::DB_ERROR'
  what():  Failed to commit a transaction to the db: MDB_BAD_TXN: Transaction must abort, has a child, or is invalid
Aborted (core dumped)

Why the mistake?