When last attachment deleted, remove ad_attachment record
When user delete last attachment and instead complete window simple close by X, - that is not in hand-in-hand with logic store attachment definitively when save attachment.
1. open record, open attachment window
2. upload attachment - when not OKd, then ad_attachment not created
3: OK it then ad_attachement created.
We suggest remove ad_attachment db record, when last attachment was removed.
this change made fully compactible approach when uploading and downloading.
Closing as potential idea - to implement this also keep in mind that attachment window can be used to add a comment, not just a file.