If you press the save button of a draggable views ordering page, the page reloads with an error instead of saving, because the weight field is empty, and null is not an allowed value in the database.
Enable the DraggableViews Demo module.
Add a DraggableViews Content node.
Go to draggableviews-demo/order
Disable javascript in your browser
Observe the weight field is empty
Press save order
Observe the error ' There was an error while saving the data. Please, try again. ' instead of the expected success message.
Either the field handler needs to set a value instead of leaving it empty, or draggableviews_views_submit needs to handle null values and fix it there before inserting in to the db.
Needs review
2.1
Code
Not sure this is the right approach but it's fixing the issue for us in our project for now...