Describe the bug

In StageRunner.cpp there's this code:

    if (m_stage->mergeMode() == Filter::WhereMergeMode::True)
    {
        if (m_viewSet.size())
            (*m_viewSet.begin())->append(*m_skips);
                return;
    }

At a glance this looks like the return is always executed after the call to append, but in reality it should be indented like this:

    if (m_stage->mergeMode() == Filter::WhereMergeMode::True)
    {
        if (m_viewSet.size())
            (*m_viewSet.begin())->append(*m_skips);
        return;
    }

Because of the way it is written, a filters.outlier with a where clause that matches 0 points and "where_merge": true will return an empty ViewSet, which will result in an empty view set being passed to all subsequent filters.

See the early return code in filters.outlier:

    PointViewSet viewSet;
    if (!inView->size())
        return viewSet;

Expected behavior
I'm not sure if the bug is in filters.outlier or StageRunner.cpp