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: f234efc407114dcf53e5398a23908c3d891a5e76
syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin