fix panic when start a node with snapshot (#673)

* fix panic when start a node with snapshot

* change the return value of evm.NewKeeper to a pointer, roll back the before change

* add changelog

* fix importer test

x/evm/keeper/keeper.go

@@ -44,14 +44,14 @@ type Keeper struct {
 // NewKeeper generates new evm module keeper
 func NewKeeper(
 	cdc *codec.Codec, storeKey sdk.StoreKey, paramSpace params.Subspace, ak types.AccountKeeper,
-) Keeper {
+) *Keeper {
 	// set KeyTable if it has not already been set
 	if !paramSpace.HasKeyTable() {
 		paramSpace = paramSpace.WithKeyTable(types.ParamKeyTable())
 	}
 
 	// NOTE: we pass in the parameter space to the CommitStateDB in order to use custom denominations for the EVM operations
-	return Keeper{
+	return &Keeper{
 		cdc:           cdc,
 		storeKey:      storeKey,
 		accountKeeper: ak,

x/evm/keeper/keeper_test.go

@@ -43,7 +43,7 @@ func (suite *KeeperTestSuite) SetupTest() {
 
 	suite.app = app.Setup(checkTx)
 	suite.ctx = suite.app.BaseApp.NewContext(checkTx, abci.Header{Height: 1, ChainID: "ethermint-3", Time: time.Now().UTC()})
-	suite.querier = keeper.NewQuerier(suite.app.EvmKeeper)
+	suite.querier = keeper.NewQuerier(*suite.app.EvmKeeper)
 	suite.address = ethcmn.HexToAddress(addrHex)
 
 	balance := sdk.NewCoins(ethermint.NewPhotonCoin(sdk.ZeroInt()))