Fixed invalid reference assignment in tests
Fixed invalid reference assignment in tests

The tx variable is assigned again later, but since it was a reference,
a copy was written on the obsolete reference and the result was some
strange behavior later in an unrelated test.

CoinGame/BCEShadow,CoinGame/NuShadowNet,CoinGame/NuShadowNet,CoinGame/BCEShadowNet,CoinGame/BCEShadowNet,CoinGame/NuShadowNet,CoinGame/BCEShadow,CoinGame/BCEShadowNet,CoinGame/NuShadowNet,CoinGame/BCEShadowNet,CoinGame/BCEShadow,CoinGame/BCEShadow,CoinGame/BCEShadowNet,CoinGame/BCEShadow,CoinGame/NuShadowNet