Fix nil pointer dereference.
Fix nil pointer dereference.

Ran into by @toddfries and brought up on IRC.

Roasbeef/btcwallet,jrick/btcwallet,btcsuite/btcwallet,Roasbeef/btcwallet,synrg-labs/btcwallet,decred/dcrwallet,jrick/dcrwallet,jrick/dcrwallet,jrick/btcwallet,decred/dcrwallet,Stash-Crypto/btcwallet,Stash-Crypto/btcwallet,synrg-labs/btcwallet,btcsuite/btcwallet