fix typo on undeclared variable xml_id
Merge pull request #2113 from yvaucher/8.0-fix-ir_model-undefined-xml_id

fix typo on undeclared variable xml_id
[FIX] fields: avoid prefetching of one2many fields

When reading a one2many field, the inverse mapping of the lines (matching m2o -> lines of corresponding record) was instantiating each line and then triggering the prefect of fields.
To improve the performances, the inverse mapping is done in sql to avoid triggering the prefetching.