Incorrect GAS calculation in System.Contract.Update.

[fyrchik]

Describe the bug
Incorrect GAS calculation in System.Contract.Update syscall. Manifest is not taken into account if script it non-null.

To Reproduce
Call ApplicationEngine.UpdateContract with non-empty script and manifest. Set GAS limit to StoragePrice * len(script).

Expected behavior
Error because of insufficient GAS.

This line AddGas(StoragePrice * (script?.Length ?? 0 + manifest?.Length ?? 0)); should probably be written as
AddGas(StoragePrice * ((script?.Length ?? 0) + (manifest?.Length ?? 0)));

[shargon]

If it's not null and it's 0 it will fault here

neo/src/neo/SmartContract/ApplicationEngine.Contract.cs

Line 76 in d1b1887

if (script.Length == 0 || script.Length > MaxContractLength)

[roman-khimov]

See nspcc-dev/neo-go#1456 for an example of this.