Help wanted
描述
Missing values in List of dicts table are pulled to the top when using ascending sorting. This might be unexpected for some users, therefore it would be convenient having an "order_null_last" or similar parameter in table meta/kwargs. I've made a hard-coded quick fix in a fork here: https://github.com/usajusaj/django-tables2/commit/ec27b7ff5915bee1fc0c431c00696599c9107311 but that's far from being a proper solution.