Error when editing node if action_on_edit is not set for field

Notice: Undefined index: action_on_edit in entityreference_prepopulate_field_access() (line 155 of /pathtodrupal/sites/all/modules/contrib/entityreference_prepopulate/entityreference_prepopulate.module).

Receiving this when editing a node with a field configured to use entityreference prepopulate that doesn't have the action_on_edit property set (because the field was created on an older version of entityreference_prepopulate that predates that setting). We should be checking the value using empty(). Patch to follow.