TypeError: unsupported operand type(s) for +=: 'NoneType' and 'datetime.timedelta'
I have my client crash when trying to view projects:
Traceback (most recent call last):
File "/trytond/protocols/jsonrpc.py", line 162, in _marshaled_dispatch
response['result'] = dispatch_method(method, params)
File "/trytond/protocols/jsonrpc.py", line 191, in _dispatch
res = dispatch(*args)
File "/trytond/protocols/dispatcher.py", line 158, in dispatch
result = rpc.result(meth(*c_args, **c_kwargs))
File "/trytond/model/modelsql.py", line 663, in read
getter_results = field.get(ids, cls, field_list, values=result)
File "/trytond/model/fields/function.py", line 91, in get
return call(names)
File "/trytond/model/fields/function.py", line 84, in call
return method(records, name)
File "/trytond/modules/project_plan/work.py", line 129, in get_function_fields
durations[work.parent.id] += durations[work_id]
TypeError: unsupported operand type(s) for +=: 'NoneType' and 'datetime.timedelta'