Fix a potential use after move

Summary:
When checking the tx inputs with CheckInputs(), the signature check
count is expected to be 0 when pvChecks is non null. This diff fixes
the current implementation which used the check variable after a move
to increment the sig check count with 0.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D7943