[dataimport] prepare_insert_entity should not crash with SQLGenObjectStore
grafted from 1079d68130e1e780791ceb2050e8a8b7a910f48d (3.22)
related to #9177565.
Document: cubicweb-doc
Title: CubicWeb documentation
Author: Logilab
Abstract: Some base documentation for CubicWeb users and developpers
Section: Apps/Programming
Format: HTML
Index: /usr/share/doc/cubicweb-documentation/index.html
Files: /usr/share/doc/cubicweb-documentation/*.html