In a multi-site setup we are sharing the taxonomy between sites by migrate. Below is a snippet of the migration yml file. In nearly every case the description is NULL and gives a "Input should be an array" error. How would I handle the description being NULL but still handling the cases when it has a value and a format?

process:
  type:
    plugin: default_value
    default_value: taxonomy_term
  tid: tid
  uuid: uuid
  langcode: langcode
  name: name
  description: description
  weight: weight
  changed: changed
  default_language: default_language
  path: path
  description/value:
    plugin: extract
    source: description
    index:
      - value
  description/format:
    plugin: extract
    source: description
    index:
      - format

Many thanks