Empty Date Time field causes TypeError

[trg]

> client.entries({"content_type"=>"<our content type>", :limit=>1000})
TypeError: no implicit conversion of nil into String

The Content Type in question has a non-required "birthdate" Date/Time field. When this field is empty on just one of the Entries of this Content Type (or perhaps was populated, then deleted -- not sure), it causes the entire lookup to fail with the error message shown above. When we populate this field with data, the error does not happen.

[pxlpnk]

@trg I just released a new version (0.3.1) that fixes the issue with non existing fields in the response.