Revert back to $data if no relation_id is set

This should fix #70 while keeping the is_array check
Merge pull request #72 from DeuxHuitHuit/issue-70

Revert back to $data if no relation_id is set
Release 1.31
Handle fields that return an array, even when it's a single value. RE: symphonycms/symphony-2#2184
Slightly better way to handle the hack...