Commit 5a81d8883 fixed the COW view deletion on module update but introduced an
error when installing a theme.
Indeed, when installing a theme, the first step is to remove the currently
installed theme from the website (by unlinking its ir.ui.view).
Commit 5a81d8883 introduced the fact that deleting an ir.ui.view during a
module uninstall also search and delete the COW views, calling
`_get_specific_views` (that expects a singleton).
When installing a theme, it calls `_theme_cleanup` which search COW views and
unlink them. If not cow view, unlink is called with an empty record set raising
the singleton error.
closesodoo/odoo#31662
Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>
Romain Derie
3f5a6f423d