Unable to synchronize after restoring namecoin wallet

[danrmiller]

Caught exception in refreshWalletData(): NoSuchMethodError: The method '[]' was called on null.
Receiver: null
Tried calling:
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:38)
#1 _objectNoSuchMethod (dart:core-patch/object_patch.dart:85)
#2 NamecoinWallet._fetchTransactionData (package:stackwallet/services/coins/namecoin/namecoin_wallet.dart:2504)

#3 NamecoinWallet.refresh (package:stackwallet/services/coins/namecoin/namecoin_wallet.dart:995)