Fix signers IInteroperable.ToStackItem

[shargon]

Close #3034

[vncoelho]

Looks good

[cschuchardt88]

Suggested change

	Scopes.HasFlag(WitnessScope.CustomContracts) ? new VM.Types.Array(referenceCounter, AllowedContracts.Select(u => new VM.Types.ByteString(u.ToArray()))) : new VM.Types.Array(referenceCounter),
	Scopes.HasFlag(WitnessScope.CustomGroups) ? new VM.Types.Array(referenceCounter, AllowedGroups.Select(u => new VM.Types.ByteString(u.ToArray()))) : new VM.Types.Array(referenceCounter),
	Scopes.HasFlag(WitnessScope.WitnessRules) ? new VM.Types.Array(referenceCounter, Rules.Select(u => u.ToStackItem(referenceCounter))) : new VM.Types.Array(referenceCounter)
	]);
	AllowedContracts != null ? new VM.Types.Array(referenceCounter, AllowedContracts.Select(u => new VM.Types.ByteString(u.ToArray()))) : new VM.Types.Array(referenceCounter),
	AllowedGroups != null ? new VM.Types.Array(referenceCounter, AllowedGroups.Select(u => new VM.Types.ByteString(u.ToArray()))) : new VM.Types.Array(referenceCounter),
	Rules != null ? new VM.Types.Array(referenceCounter, Rules.Select(u => u.ToStackItem(referenceCounter))) : new VM.Types.Array(referenceCounter)
	]);

The crash is happening because AllowedContracts, AllowedGroups and Rules is null, and doing .Select() will still cause a crash with those flags set. Take in count ApplicationEngine.Run and Dynamic Scripts.

[cschuchardt88]

@shargon @roman-khimov @AnnaShaleva
This should work now.

[shargon]

The flags are used in other serializable methods, so we should fix the flags if are wrong in cli

[cschuchardt88]

Are you able to do Rules?.Select()? For example new VM.Types.Array(referenceCounter, Rules?.Select(u => u.ToStackItem(referenceCounter)))

But look at Call Stack->NullException

   at System.Linq.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument)
   at System.Linq.Enumerable.Select[TSource,TResult](IEnumerable`1 source, Func`2 selector)
   at Neo.Network.P2P.Payloads.Signer.Neo.SmartContract.IInteroperable.ToStackItem(ReferenceCounter referenceCounter)
   at Neo.SmartContract.ApplicationEngine.Convert(Object value)
   at Neo.SmartContract.ApplicationEngine.<Convert>b__95_0(Object p)