Warmup: State::LoadingKVPairs keeps scanning when NMVB occurs

void LoadValueCallback::callback(CacheLookup& lookup) {

    // If not value-eviction (LoadingData), then skip attempting to check for

    // value already resident, given we assume nothing has been loaded for this

    // document yet.

    if (warmupState != WarmupState::State::LoadingData) {

        setStatus(cb::engine_errc::success);

        return;

    }

    // Prepared SyncWrites are ignored in the normal LoadValueCallback -

    // they are handled in an earlier warmup phase so return

    // cb::engine_errc::key_already_exists to indicate this key should be

    // skipped.

    if (lookup.getKey().isPrepared()) {

        setStatus(cb::engine_errc::key_already_exists);

        return;

    }

    VBucketPtr vb = vbuckets.getBucket(lookup.getVBucketId());

    if (!vb) {

>>>> MISSING 

        return;

    }