Validation fail after preview

Problem/Motivation

On our project, we have a preview button for content. When we set the group(s) and "group" visibility option, pressed the preview button, and went back to editing I received the error "group visibility is not allowed". It is because of the disabled group option.

Steps to reproduce

- Enable preview for nodes
- On adding node set group with "group" visibility option
- Press the Preview button
- Go back to editing process

Proposed resolution

In the "social_group_field_widget_single_element_form_alter" instead of getting "groups" from form values use the user input, as form values do not always exist after the preview.