HStore{Map,List} don't support NULL values #283
Description
PG's hstore supports having NULL as values. However, this is not supported by postgresql-simple.
Unfortunately this isn't only a parser problem either, as HStore{Map,List} expose their constructor and internals, meaning that it would be a breaking change to make them to hold Map Text (Maybe Text). I guess there should be be a new module and type along the lines of NullableHStore{Map,List} to avoid breakage