text: Title: Captured subproc: AttributeError: 'NoneType' object has no attribute 'pid'
  Body: xonsh 0.19.2
  
  In case of running unknown command:
  ```xsh
  $XONSH_SHOW_TRACEBACK = True
  !(qwe qwe)
  
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
    File "/Users/pc/.local/xonsh-env/lib/python3.12/site-packages/xonsh/main.py", line 273, in _pprint_displayhook
      printed_val = pretty(value)
                    ^^^^^^^^^^^^^
    File "/Users/pc/.local/xonsh-env/lib/python3.12/site-packages/xonsh/lib/pretty.py", line 129, in pretty
      printer.pretty(obj)
    File "/Users/pc/.local/xonsh-env/lib/python3.12/site-packages/xonsh/lib/pretty.py", line 399, in pretty
      return _default_pprint(obj, self, cycle)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "/Users/pc/.local/xonsh-env/lib/python3.12/site-packages/xonsh/lib/pretty.py", line 518, in _default_pprint
      _repr_pprint(obj, p, cycle)
    File "/Users/pc/.local/xonsh-env/lib/python3.12/site-packages/xonsh/lib/pretty.py", line 727, in _repr_pprint
      output = repr(obj)
               ^^^^^^^^^
    File "/Users/pc/.local/xonsh-env/lib/python3.12/site-packages/xonsh/procs/pipelines.py", line 199, in __repr__
      s += ",\n  ".join(
           ^^^^^^^^^^^^^
    File "/Users/pc/.local/xonsh-env/lib/python3.12/site-packages/xonsh/procs/pipelines.py", line 202, in <genexpr>
      if debug or getattr(self, a) is not None
                  ^^^^^^^^^^^^^^^^
    File "/Users/pc/.local/xonsh-env/lib/python3.12/site-packages/xonsh/procs/pipelines.py", line 730, in pid
      return self.proc.pid
             ^^^^^^^^^^^^^
  AttributeError: 'NoneType' object has no attribute 'pid'
  ```
  
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