OG entity reference widget doesn't save values when used in Page Manager access dialog

[miloskroulik]

Can be reproduced with:

1. Enable latest OG an Page Manager module (part of Ctools)
2. Create some entities which are used as groups
3. Create a new page and in access settings select User user: Group membership Field
4. Try to select some of your groups and save the form
5. The values aren't saved

It works fine, when you select other widget, such as Select.