In the rare case that someone may take an online seeded wallet offline. This will make sure that the blockchain headers do not interfere with the offline height calculation. Earlier in the file, it checks on every refresh if there is a blockchain_headers_offline file and if it is online. If so, it removes the empty headers file and replaces it with the renamed offline headers file. This allows people to retain confirms and timestamps in history in any combination of offline > online or online > offline, and offline updating or not.