[Dbix-class] NULL values and DBIx::Class::InflateColumn::DateTime

[Will Hawes]

The InflateColumn::DateTime helper currently throws "Invalid date
format:  " for rows that contain NULL, even if the column info has
is_nullable => 1. The docs show that either default_value =>
'0000-00-00' or datetime_undef_if_invalid => 1 could be used to work
around this, but bypassing inflation completely based on the presence
of is_nullable => 1 would be trivial and probably more sensible. Happy
to patch if others are in agreement, what do you think?