[wallet] Fix potential memory leak in CreateWalletFromFile
[wallet] Fix potential memory leak in CreateWalletFromFile

Fix proposed by ryanofsky in
https://github.com/bitcoin/bitcoin/pull/12647#discussion_r174875670

chaincoin/chaincoin,chaincoin/chaincoin,chaincoin/chaincoin,chaincoin/chaincoin,chaincoin/chaincoin,chaincoin/chaincoin