fix(baseapp): allow empty consensus params (#18531)

Co-authored-by: Aleksandr Bezobchuk <alexanderbez@users.noreply.github.com>

baseapp/baseapp.go

@@ -522,7 +522,11 @@ func (app *BaseApp) GetConsensusParams(ctx sdk.Context) cmtproto.ConsensusParams
 
 	cp, err := app.paramStore.Get(ctx)
 	if err != nil {
-		panic(fmt.Errorf("consensus key is nil: %w", err))
+		// This could happen while migrating from v0.45/v0.46 to v0.50, we should
+		// allow it to happen so during preblock the upgrade plan can be executed
+		// and the consensus params set for the first time in the new format.
+		app.logger.Error("failed to get consensus params", "err", err)
+		return cmtproto.ConsensusParams{}
 	}
 
 	return cp

baseapp/baseapp_test.go

@@ -720,6 +720,17 @@ func TestGetMaximumBlockGas(t *testing.T) {
 	require.Panics(t, func() { suite.baseApp.GetMaximumBlockGas(ctx) })
 }
 
+func TestGetEmptyConsensusParams(t *testing.T) {
+	suite := NewBaseAppSuite(t)
+	_, err := suite.baseApp.InitChain(&abci.RequestInitChain{})
+	require.NoError(t, err)
+	ctx := suite.baseApp.NewContext(true)
+
+	cp := suite.baseApp.GetConsensusParams(ctx)
+	require.Equal(t, cmtproto.ConsensusParams{}, cp)
+	require.Equal(t, uint64(0), suite.baseApp.GetMaximumBlockGas(ctx))
+}
+
 func TestLoadVersionPruning(t *testing.T) {
 	logger := log.NewNopLogger()
 	pruningOptions := pruningtypes.NewCustomPruningOptions(10, 15)