[master-2.x] Fix Transaction verify

[Qiao-Jin]

Close #1999

[ProDog]

Tesed OK.

request:

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "sendrawtransaction",
  "params": ["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"]
}

result:

{
    "jsonrpc": "2.0",
    "id": 1,
    "error": {
        "code": -504,
        "message": "Block or transaction validation failed."
    }
}

[shargon]

What about add the try/catch in

neo/neo/Network/P2P/Payloads/Transaction.cs

Line 99 in a3217ea

Output = tx.Outputs[p.PrevIndex]

and return null

[ZhangTao1596]

base.Verify() before check NetworkFee?
No need add try/catch in Transaction.Verify. It will be check in IsDoubleSpend.

neo/neo/Persistence/Helper.cs

Lines 104 to 114 in e18d431

	public static bool IsDoubleSpend(this IPersistence persistence, Transaction tx)
	{
	if (tx.Inputs.Length == 0) return false;
	foreach (var group in tx.Inputs.GroupBy(p => p.PrevHash))
	{
	UnspentCoinState state = persistence.UnspentCoins.TryGet(group.Key);
	if (state == null) return true;
	if (group.Any(p => p.PrevIndex >= state.Items.Length || state.Items[p.PrevIndex].HasFlag(CoinState.Spent)))
	return true;
	}
	return false;

Or we can split UTXO verify and witness verify. We need UTXO verify before get references.

[Qiao-Jin]

What about add the try/catch in

neo/neo/Network/P2P/Payloads/Transaction.cs

Line 99 in a3217ea

Output = tx.Outputs[p.PrevIndex]

and return null

Fixed

[ProDog]

Tested OK.

[Qiao-Jin]

@shargon @erikzhang Can we merge this one?