Fix to switch mimetype if the new file has a different mimetype.
Updated based on comment.
Change to use file mimetype not OBJ mimetype incase it's called when the OBJ isn't set or isn't updated.
Fixed variable reference.
remove DSM.
Merge pull request #100 from matthewperry/7.x-INT-451

Fix to switch mimetype if the new file has a different mimetype.