[FIX] base_sparse_field,mail: handle None _instanciate_attrs override

The parent was expected to return a dict, but it can also return None in some
cases. When that happens, the overrides were crashing because it is impossible
to assign a key/val to None.

Note that using `if` conditions like this also prevents from writing on the dict
if it is existing but empty, but due to the definition of the parent, if there
is a dict, it will not be empty.

closes #38168

Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>

addons/base_sparse_field/models/models.py

@@ -58,7 +58,7 @@ def _reflect_model(self, model):
 
     def _instanciate_attrs(self, field_data):
         attrs = super(IrModelFields, self)._instanciate_attrs(field_data)
-        if field_data.get('serialization_field_id'):
+        if attrs and field_data.get('serialization_field_id'):
             serialization_record = self.browse(field_data['serialization_field_id'])
             attrs['sparse'] = serialization_record.name
         return attrs

addons/mail/models/ir_model.py

@@ -111,6 +111,6 @@ def _reflect_field_params(self, field):
 
     def _instanciate_attrs(self, field_data):
         attrs = super(IrModelField, self)._instanciate_attrs(field_data)
-        if field_data.get('tracking'):
+        if attrs and field_data.get('tracking'):
             attrs['tracking'] = field_data['tracking']
         return attrs