message: Make sure to init PostVS buffers before fetching
  * Normally a mesh rendering replay output would do this implicitly when
  an event is selected, but if accessing purely through script this may
  not happen, so we should initialise it ourselves here.
  * If it's already init'd, it's almost free to call again.
diff: @@ -356,6 +356,8 @@ MeshFormat ReplayController::GetPostVSData(uint32_t instID, MeshDataStage stage)
  instID = RDCMIN(instID, draw->numInstances - 1);
  + m_pDevice->InitPostVSBuffers(draw->eventId);
  +
  return m_pDevice->GetPostVSBuffers(draw->eventId, instID, stage);
  }
  