Search on resource model with empty resource field
If the resource field is not linked to a record (id: -1), the search added by b2bccf9f45a3 crashes with: ``` Traceback (most recent call last): File "trytond/protocols/wrappers.py", line 197, in wrapper return func(request, pool, *args, **kwargs) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "trytond/protocols/dispatcher.py", line 196, in _dispatch result = rpc.result(meth(*c_args, **c_kwargs)) ^^^^^^^^^^^^^^^^^^^^^^^^^ File "trytond/ir/resource.py", line 83, in search if record.resource and record.resource.id >= 0: ^^^^^^^^^^^^^^^^^^ AttributeError: 'str' object has no attribute 'id' ```
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