Update beforevalidate to enable status updates

validating the status with php's empty method makes it impossible to update the status of a record to 0. 
usecase: $statuses = array(-1, 0, 1); // -1 = deleted, 0 = archived, 1 = active/Default
result: "manual" change from active to archived is not possible
Merge pull request #3 from gutschik/master

Update beforevalidate to enable status updates to 0