[FIX] Temporary fix o2m editable list onchange bug

The edition is cancelled when an onchange happen in o2m
while editing.

Editor.shelve() and Editor.unshelve() are prepared but
doesn't work. Would need help of xmo.
[FIX] prevent o2m onchange to fail

Still need to properly fix it, currently doesn't apply the onchange
Merge pull request #5 from odoo-dev/master-apiculture-o2m-onchange-fme

[FIX] Temporary fix o2m editable list onchange bug