m2o convert_domain_path: can not concatenate none and string when path is none
In a model has _history=True, when try to read the history, I get the traceback: ``` 104152 140692552353536 [2023-04-27 09:14:16,843] ERROR trytond.protocols.dispatcher <class 'trytond.pool.project.work'>.read(*([47273], ['active', ....}), **{}) from raimon@127.0.0.1/nan64nan/ Traceback (most recent call last): File "/home/raimon/projectes/nandev2/nan64nan/trytond/trytond/protocols/dispatcher.py", line 195, in _dispatch result = rpc.result(meth(*c_args, **c_kwargs)) File "/home/raimon/projectes/nandev2/nan64nan/trytond/trytond/model/modelsql.py", line 932, in read getter_results = field.get( File "/home/raimon/projectes/nandev2/nan64nan/trytond/trytond/model/fields/function.py", line 26, in wrapper return func(self, *args, **kwargs) File "/home/raimon/projectes/nandev2/nan64nan/trytond/trytond/model/fields/function.py", line 136, in get return call(names) File "/home/raimon/projectes/nandev2/nan64nan/trytond/trytond/model/fields/function.py", line 130, in call return method(records, name) File "/home/raimon/projectes/nandev2/nan64nan/trytond/trytond/modules/project/work.py", line 448, in get_total works = cls.search([ File "/home/raimon/projectes/nandev2/nan64nan/trytond/trytond/model/modelsql.py", line 1504, in search tables, expression = cls.__search_query(domain, count, query, order) File "/home/raimon/projectes/nandev2/nan64nan/trytond/trytond/model/modelsql.py", line 1423, in __search_query tables, expression = cls.search_domain(domain) File "/home/raimon/projectes/nandev2/nan64nan/trytond/trytond/model/modelsql.py", line 1643, in search_domain expression = convert(domain) File "/home/raimon/projectes/nandev2/nan64nan/trytond/trytond/model/modelsql.py", line 1639, in convert return And((convert(d) for d in ( File "/home/raimon/projectes/nandev2/nan64nan/trytond/trytond/model/modelsql.py", line 1639, in <genexpr> return And((convert(d) for d in ( File "/home/raimon/projectes/nandev2/nan64nan/trytond/trytond/model/modelsql.py", line 1630, in convert expression = field.convert_domain(domain, tables, cls) File "/home/raimon/projectes/nandev2/nan64nan/trytond/trytond/model/fields/field.py", line 200, in wrapper return func(*args, **kwargs) File "/home/raimon/projectes/nandev2/nan64nan/trytond/trytond/model/fields/many2one.py", line 235, in convert_domain return self.convert_domain_path( File "/home/raimon/projectes/nandev2/nan64nan/trytond/trytond/model/fields/many2one.py", line 136, in convert_domain_path where.append(path_column.like(path + '%')) TypeError: unsupported operand type(s) for +: 'NoneType' and 'str' ``` In see that in database som history rows, path is none. Example: ``` id | path | create_date -------+--------------+---------------------------- 47273 | | 2022-10-11 15:19:41.924071 47273 | 30856/47273/ | 2022-10-11 15:19:41.924071 ... ```
issue