object_to statement in persistent model causes a crash

Create this model

a = 2
a to file 'a.yaml'

in a file test.vm and run it with texts script -f test.vm. Then texts session -u <uuid> crashes with this error:

Traceback (most recent call last):
  File "vre-language/src/virtmat/language/utilities/errors.py", line 276, in wrapper
    return func(*args, **kwargs)
  File "vre-language/src/virtmat/language/cli/run_session.py", line 74, in main
    mgr = SessionManager(lp_obj, uuid=clargs.uuid, autorun=clargs.autorun,
  File "vre-language/src/virtmat/language/interpreter/session_manager.py", line 550, in __init__
    self.session = Session(lpad, create_new=True, **kwargs)
  File "vre-language/src/virtmat/language/interpreter/session_manager.py", line 110, in __init__
    self.process_models('print(true)')
  File "vre-language/src/virtmat/language/interpreter/session_manager.py", line 193, in process_models
    strns, paths, varies = self._process_strings_paths(model_str, model_path)
  File "vre-language/src/virtmat/language/interpreter/session_manager.py", line 224, in _process_strings_paths
    model_str_ = self._expand_reuse(model_str)
  File "vre-language/src/virtmat/language/interpreter/session_manager.py", line 232, in _expand_reuse
    local_var_names = set(self._get_all_var_names())
  File "vre-language/src/virtmat/language/interpreter/session_manager.py", line 325, in _get_all_var_names
    return set(names)
  File "vre-language/src/virtmat/language/interpreter/session_manager.py", line 324, in <genexpr>
    names = (o for n in nodes for t in n['spec']['_tasks'] for o in t['outputs'])
KeyError: 'outputs'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "python-3.10.12/bin/texts", line 8, in <module>
    sys.exit(texts())
  File "vre-language/src/virtmat/language/cli/__init__.py", line 25, in texts
    clargs.func(clargs)
  File "vre-language/src/virtmat/language/utilities/errors.py", line 302, in wrapper
    raise RuntimeError('non-handled exception') from err
RuntimeError: non-handled exception