[FIX] orm: don't crash on index creation

For existing installations, creating indices might not always be
possible, e.g. if you have a Text/Char field that has an index=True
set on it in a field override and pre-existing rows longer than
the pg supported size , the index creation will fail.

Instead of failing miserably during the schema modification, simply
log the problem instead and keep going.

closes odoo/odoo#32442

Signed-off-by: Raphael Collet (rco) <rco@openerp.com>