renku run workflowfile broken without inputs/outputs

[Panaetius]

a user wanted to use renku run in a new project and hit several roadblocks. They used renku run inside the workflow file, which doesn't work.

additionally they tried to use renku.api in their script without having the inputs/outputs specified in the workflow file. so their workflow has ho inputs/outputs in the wf file.
this results in the following error:

Traceback (most recent call last):
  File "/home/user/.pyenv/versions/renku-python/bin/renku", line 6, in <module>
    sys.exit(cli())
  File "/home/user/.pyenv/versions/3.8.13/envs/renku-python/lib/python3.8/site-packages/click/core.py", line 1130, in __call__
    return self.main(*args, **kwargs)
  File "/home/user/DEV/ETH/renku-python/renku/ui/cli/exception_handler.py", line 139, in main
    self._handle_github()
  File "/home/user/DEV/ETH/renku-python/renku/ui/cli/exception_handler.py", line 171, in _handle_github
    getattr(self, "_process_" + value)()
  File "/home/user/DEV/ETH/renku-python/renku/ui/cli/exception_handler.py", line 131, in main
    return super().main(*args, **kwargs)
  File "/home/user/DEV/ETH/renku-python/renku/ui/cli/exception_handler.py", line 90, in main
    return super().main(*args, **kwargs)
  File "/home/user/.pyenv/versions/3.8.13/envs/renku-python/lib/python3.8/site-packages/click/core.py", line 1055, in main
    rv = self.invoke(ctx)
  File "/home/user/.pyenv/versions/3.8.13/envs/renku-python/lib/python3.8/site-packages/click/core.py", line 1657, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/user/.pyenv/versions/3.8.13/envs/renku-python/lib/python3.8/site-packages/click/core.py", line 1404, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/user/.pyenv/versions/3.8.13/envs/renku-python/lib/python3.8/site-packages/click/core.py", line 760, in invoke
    return __callback(*args, **kwargs)
  File "/home/user/DEV/ETH/renku-python/renku/ui/cli/run.py", line 626, in run
    run_workflow_file_command(no_commit=no_commit, commit_only=commit_only)
  File "/home/user/DEV/ETH/renku-python/renku/command/command_builder/command.py", line 250, in execute
    output = self._operation(*args, **kwargs)  # type: ignore
  File "/home/user/.pyenv/versions/3.8.13/envs/renku-python/lib/python3.8/site-packages/inject/__init__.py", line 342, in injection_wrapper
    return sync_func(*args, **kwargs)
  File "pydantic/decorator.py", line 40, in pydantic.decorator.validate_arguments.validate.wrapper_function
  File "pydantic/decorator.py", line 134, in pydantic.decorator.ValidatedFunction.call
  File "pydantic/decorator.py", line 206, in pydantic.decorator.ValidatedFunction.execute
  File "/home/user/DEV/ETH/renku-python/renku/core/workflow/workflow_file.py", line 81, in run_workflow_file
    execute_workflow_graph(dag=graph.workflow_graph, provider=provider, workflow_file_plan=workflow)
  File "/home/user/.pyenv/versions/3.8.13/envs/renku-python/lib/python3.8/site-packages/inject/__init__.py", line 342, in injection_wrapper
    return sync_func(*args, **kwargs)
  File "/home/user/DEV/ETH/renku-python/renku/core/workflow/execute.py", line 112, in execute_workflow_graph
    activity_collection = WorkflowFileActivityCollection.from_activities(
  File "/home/user/.pyenv/versions/3.8.13/envs/renku-python/lib/python3.8/site-packages/inject/__init__.py", line 342, in injection_wrapper
    return sync_func(*args, **kwargs)
  File "/home/user/DEV/ETH/renku-python/renku/domain_model/provenance/activity.py", line 332, in from_activities
    association = Association(agent=activities[0].association.agent, id=Association.generate_id(id), plan=plan)
IndexError: list index out of range