Fix #1834

[shargon]

We need to ensure that all the indexes can fit in LastSeenMessage, if we use a integer type, we have the half available chain.

Also, if heigh it's 0, LastSeenMessage?.Count(p => Block.Index > 0 && p.Value < (Block.Index - 1)) ?? 0; it will produce an integer overflow, and the condition always will be true.

[erikzhang]

uint is better?

[shargon]

Yes, it's better, but the consensus UT use -1, we can fix the UT and change to uint

[shargon]

The problem is that ConsensusService use Blockchain.Singleton and it has 1 Height. So it can't meet this UT

neo/tests/neo.UnitTests/Consensus/UT_Consensus.cs

Lines 169 to 180 in ca13358

	mockContext.Object.ChangeViewPayloads[mockContext.Object.MyIndex] = null;
	Console.WriteLine("Forcing Failed nodes for recovery request... ");
	mockContext.Object.CountFailed.Should().Be(0);
	mockContext.Object.LastSeenMessage.Clear();
	foreach (var validator in mockContext.Object.Validators)
	{
	mockContext.Object.LastSeenMessage[validator] = -1;
	}
	mockContext.Object.CountFailed.Should().Be(7);
	Console.WriteLine("\nWaiting for recovery due to failed nodes... ");
	var backupOnRecoveryDueToFailedNodes = subscriber.ExpectMsg<LocalNode.SendDirectly>();
	var recoveryPayload = (ConsensusPayload)backupOnRecoveryDueToFailedNodes.Inventory;

[shargon]

I think that now it's better, because if LastSeen doesn't contain the pubKey, it will be counted as failed.

[erikzhang]

Test need to be fixed.