fuzz: fix vector size problem in system fuzzer
fuzz: fix vector size problem in system fuzzer

Co-authored-by: Pieter Wuille <pieter.wuille@gmail.com>

Former-commit-id: fd817f3712c696fb9590373479c7909428bc00c5
syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin