`_add_manual_models` builds Python model classes for custom ("manual") `ir.model` records with a raw `SELECT *` on the `ir_model` table, then hands each row to `_instanciate_attrs`, which reads a fixed list of expected columns (`model`, `name`, `abstract`, `transient`, `order`, `fold_name`, `info`) via dict subscription (`model_data['xxx']`).

This assumes every one of these fields is always backed by a real database column. That assumption breaks whenever a field originally declared as stored on `ir.model` gets redeclared as non-stored (`store=False`) by another module inheriting the same model: Odoo correctly drops the now-unneeded column during that module's `_auto_init()`, but any code still doing `SELECT *` on the table no longer gets that key in the result row, and the subscript access raises a bare `KeyError`. This aborts the *entire* registry load, for every model in the database, not just the one whose field changed -- because `_add_manual_models` runs once per registry load and any database with at least one manual/custom model exercises it.

This is exactly the scenario introduced by 267bec440d56 ("[IMP] base: add IrModel.abstract field"): it added a new, plain stored `abstract` field on `ir.model`. `web_studio` has independently defined its own `abstract` field on `ir.model` since 2016 (ac1129f6577), as a computed, `store=False` field. Once both are loaded together, Odoo's field- merging logic settles on the `store=False` definition, so `_auto_init()` drops the `abstract` column -- and any database that also has at least one manual model (built through Studio, or via a module that dynamically generates SQL-view-backed models) then fails to boot its registry at all:

    File ".../odoo/orm/model_classes.py", line 554, in _add_manual_models
        attrs = env['ir.model']._instanciate_attrs(model_data)
    File ".../odoo/addons/base/models/ir_model.py", line 487, in _instanciate_attrs
        '_abstract': bool(model_data['abstract']),
    KeyError: 'abstract'

Fix `_instanciate_attrs` to fall back to a sane default instead of assuming the column exists. This doesn't just patch the `base`/ `web_studio` collision -- it hardens `_add_manual_models` against any future field made non-stored by an inheriting module, which is otherwise a silent, whole-database-breaking failure with no visible relation to whichever module actually changed the field.

A companion fix removing web_studio's now-redundant override (the actual root cause of the collision) is proposed separately.

Steps to reproduce:
1. Install `base` and `web_studio` together (or in either order) --
   Odoo's field-merging settles on web_studio's `store=False`
   definition, but leaves the `abstract` column physically in place;
   it is not dropped automatically.
2. Have at least one manual model in the database (`state='manual'`
   on `ir.model`, e.g. created through Settings > Technical > Models).
3. Actually remove the now-orphaned `abstract` column -- e.g. via the
   OCA `database_cleanup` module's column-purge wizard
   (`cleanup.purge.wizard.column`), which explicitly targets exactly
   this kind of column (computed + non-stored fields are excluded
   from its "keep" list, so `abstract` gets flagged and dropped).
4. Restart Odoo / reload the registry: it fails to boot entirely with
   a KeyError on that field name, for every model, not just the one
   whose owning module changed.


Related: odoo/enterprise#123572



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