[FIX] odoo: Import data with falsy many2one fields

Steps to reproduce:

- Export a partner with country set to False, using EXCELL
- Try to import it with the xls file

Bug:

It raised: "No matching record found for name 'False' in field 'Country' at row 2"

opw:2080376

closes odoo/odoo#38220

Signed-off-by: Simon Goffin (sig) <sig@openerp.com>

odoo/addons/base/models/ir_fields.py

@@ -318,6 +318,8 @@ class IrFieldsConverter(models.AbstractModel):
         RelatedModel = self.env[field.comodel_name]
         if subfield == '.id':
             field_type = _(u"database id")
+            if isinstance(value, str) and not self._str_to_boolean(model, field, value)[0]:
+                return False, field_type, warnings
             try: tentative_id = int(value)
             except ValueError: tentative_id = value
             try:
@@ -332,6 +334,8 @@ class IrFieldsConverter(models.AbstractModel):
                     {'moreinfo': action})
         elif subfield == 'id':
             field_type = _(u"external id")
+            if not self._str_to_boolean(model, field, value)[0]:
+                return False, field_type, warnings
             if '.' in value:
                 xmlid = value
             else:
@@ -340,6 +344,8 @@ class IrFieldsConverter(models.AbstractModel):
             id = self.env['ir.model.data'].xmlid_to_res_id(xmlid, raise_if_not_found=False) or None
         elif subfield is None:
             field_type = _(u"name")
+            if value == '':
+                return False, field_type, warnings
             flush()
             ids = RelatedModel.name_search(name=value, operator='=')
             if ids: