Bad exit from log from RE

Summary

    [00:00:00] FAILURE bootstrap/gnu-config.bst: Failed to query action cache: StatusCode.INVALID_ARGUMENT (Invalid instance name: [development-emea-1])
    ======================================================================

[20:42:28][--:--:--][        ][    main:core activity                 ] BUG     'NoneType' object has no attribute 'was_workspaced'

    Traceback (most recent call last):
      File "/usr/lib64/python3.7/asyncio/events.py", line 88, in _run
        self._context.run(self._callback, *self._args)
      File "/home/will/projects/buildstream/buildstream/src/buildstream/_scheduler/scheduler.py", line 458, in real_schedule
        self._sched_queue_jobs()
      File "/home/will/projects/buildstream/buildstream/src/buildstream/_scheduler/scheduler.py", line 406, in _sched_queue_jobs
        queue.enqueue(elements)
      File "/home/will/projects/buildstream/buildstream/src/buildstream/_scheduler/queues/queue.py", line 184, in enqueue
        self._enqueue_element(elt)
      File "/home/will/projects/buildstream/buildstream/src/buildstream/_scheduler/queues/queue.py", line 367, in _enqueue_element
        status = self.status(element)
      File "/home/will/projects/buildstream/buildstream/src/buildstream/_scheduler/queues/artifactpushqueue.py", line 39, in status
        if element._skip_push():
      File "/home/will/projects/buildstream/buildstream/src/buildstream/element.py", line 1769, in _skip_push
        if self.__get_tainted():
      File "/home/will/projects/buildstream/buildstream/src/buildstream/element.py", line 2409, in __get_tainted
        workspaced = self.__artifact.get_metadata_workspaced()
      File "/home/will/projects/buildstream/buildstream/src/buildstream/_artifact.py", line 341, in get_metadata_workspaced
        self._metadata_workspaced = artifact.was_workspaced
    AttributeError: 'NoneType' object has no attribute 'was_workspaced'

Odd failure after looking at logs of failed RE build the server was not called development-emea-1

Steps to reproduce

add instance-name: development-emea-1 to the remote-execution: sections eg. action-cache-service: when the service is called ""

then look at logs then ctl+C

What is the current bug behavior?

un recoverable crash and track back as above.

What is the expected correct behavior?

graceful exit

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