message: [XLA:Python] Check for c_api being None during LocalComputation's finalizer.
  During process shutdown, it seems sometimes c_api can be None, leading to noisy warnings.
diff: @@ -757,7 +757,8 @@ class LocalComputation(object):
  return [out.to_py() for out in self.ExecutePerReplica(arguments)]
  def __del__(self):
  - # Ensure a reference to C-based destructor for use in __del__.
  + # Python may have freed c_api first.
  + if c_api and self._c_computation:
  if self._is_compiled:
  self._backend.delete_executable(self._c_computation)
  else:
  