Bug: _force_audit method is not checking for whether the column is a valid column

Not everything that is returned by `get_columns` is an actual valid column name.

When using `DBIx::Class::Helper::ResultSet::CorrelateRelationship` the data is also stored together with columns, but it is not a valid column.

Trying to call `column_info` on an invalid column results in death by "column does not exist".

Second commit simply fixes a small issue where you can have `force_audit_log_column => 0`, which is, of course, silly, it is a possibility. However, that would pass `defiend`, as the key is defined, just set to zero.