Possibly not handling threads correctly in results step

Possibly all tests of the results step end with the following:

```python
threadexception.py:73: PytestUnhandledThreadExceptionWarning: Exception in thread Thread-1

Traceback (most recent call last):
File "/opt/conda/lib/python3.9/threading.py", line 980, in _bootstrap_inner
self.run()
File "/opt/conda/lib/python3.9/threading.py", line 917, in run
self._target(*self._args, **self._kwargs)
File "/home/jovyan/.local/lib/python3.9/site-packages/aiidalab_widgets_base/process.py", line 763, in _monitor_process
process = orm.load_node(process_uuid)
File "/opt/conda/lib/python3.9/site-packages/aiida/orm/utils/loaders.py", line 207, in load_node
return load_entity(
File "/opt/conda/lib/python3.9/site-packages/aiida/orm/utils/loaders.py", line 93, in load_entity
return entity_loader.load_entity(
File "/opt/conda/lib/python3.9/site-packages/aiida/orm/utils/loaders.py", line 399, in load_entity
entity = builder.one()[0]
File "/opt/conda/lib/python3.9/site-packages/aiida/orm/querybuilder.py", line 1140, in one
res = self.all()
File "/opt/conda/lib/python3.9/site-packages/aiida/orm/querybuilder.py", line 1120, in all
matches = list(self.iterall(batch_size=batch_size))
File "/opt/conda/lib/python3.9/site-packages/aiida/orm/querybuilder.py", line 1086, in iterall
item[i] = self._get_aiida_entity_res(item_entry)
File "/opt/conda/lib/python3.9/site-packages/aiida/orm/querybuilder.py", line 1031, in _get_aiida_entity_res
return convert.get_orm_entity(value)
File "/opt/conda/lib/python3.9/functools.py", line 888, in wrapper
return dispatch(args[0].__class__)(*args, **kw)
File "/opt/conda/lib/python3.9/site-packages/aiida/orm/convert.py", line 118, in _
node_class = load_node_class(backend_entity.node_type)
File "/opt/conda/lib/python3.9/site-packages/aiida/storage/psql_dos/orm/nodes.py", line 122, in node_type
return self.model.node_type
File "/opt/conda/lib/python3.9/site-packages/aiida/storage/psql_dos/orm/utils.py", line 81, in __getattr__
if self.is_saved() and self._is_mutable_model_field(item) and not self._in_transaction():
File "/opt/conda/lib/python3.9/site-packages/aiida/storage/psql_dos/orm/utils.py", line 106, in is_saved
with self.session.no_autoflush:
File "/opt/conda/lib/python3.9/site-packages/aiida/storage/psql_dos/orm/utils.py", line 64, in session
return self._backend.get_session()
File "/opt/conda/lib/python3.9/site-packages/aiida/storage/psql_dos/backend.py", line 182, in get_session
raise ClosedStorage(str(self))
aiida.common.exceptions.ClosedStorage: SqliteDosStorage[/tmp/pytest-of-jovyan/pytest-191/bcfbb094bd18b1a09601c918ccbb93c10/.aiida/f7b938d84e6d8336ab6ee0f4846a5f6f/storage]: closed,
```

This is coming from the process monitor. Either we are not handling it properly in tests, mishandling it in the app, or, since we rely on AWB's `ProcessMonitor`, using a thread-unstable widget.