*: fix ineffassign where the value should really be used

Found with GoReportCard.

pkg/core/interop_neo.go

@@ -89,7 +89,7 @@ func contractCreate(ic *interop.Context) error {
 		return err
 	}
 	contract, err := ic.DAO.GetContractState(newcontract.ScriptHash())
-	if contract != nil {
+	if contract != nil && err == nil {
 		return errors.New("contract already exists")
 	}
 	id, err := ic.DAO.GetAndUpdateNextContractID()

pkg/core/interop_system_test.go

@@ -733,6 +733,7 @@ func TestContractUpdate(t *testing.T) {
 
 		// updated contract should have new scripthash
 		actual, err := ic.DAO.GetContractState(cs.ScriptHash())
+		require.NoError(t, err)
 		expected := &state.Contract{
 			ID:       cs.ID,
 			Script:   cs.Script,

pkg/core/native_policy_test.go

@@ -160,6 +160,7 @@ func TestBlockedAccounts(t *testing.T) {
 		require.NoError(t, chain.persist())
 
 		res, err = invokeNativePolicyMethod(chain, "unblockAccount", account.BytesBE())
+		require.NoError(t, err)
 		checkResult(t, res, stackitem.NewBool(true))
 
 		accounts, err = chain.contracts.Policy.GetBlockedAccountsInternal(chain.dao)
@@ -183,11 +184,13 @@ func TestBlockedAccounts(t *testing.T) {
 
 		// unblock
 		res, err = invokeNativePolicyMethod(chain, "unblockAccount", account.BytesBE())
+		require.NoError(t, err)
 		checkResult(t, res, stackitem.NewBool(true))
 		require.NoError(t, chain.persist())
 
 		// unblock the same account should fail as we don't have it blocked
 		res, err = invokeNativePolicyMethod(chain, "unblockAccount", account.BytesBE())
+		require.NoError(t, err)
 		checkResult(t, res, stackitem.NewBool(false))
 		require.NoError(t, chain.persist())
 	})