fix backwards compatibility error with get_settings

[RaynorChavez]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  Bug fix

• What is the current behavior? (You can also link to an open issue here)
  users switching from 2.11 to 2.12 and using the get_settings api endpoint will get an error

{
  "message": "[{\"loc\": [\"videoPreprocessing\"], \"msg\": \"none is not an allowed value\", \"type\": \"type_error.none.not_allowed\"}, {\"loc\": [\"audioPreprocessing\"], \"msg\": \"none is not an allowed value\", \"type\": \"type_error.none.not_allowed\"}]",
  "code": "invalid_argument",
  "type": "invalid_request",
  "link": ""
}

other api endpoints unaffected

• What is the new behavior (if this is a feature change)?
  2.11 indexes upgraded to 2.12 will no longer get this error

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  No

• Have unit tests been run against this PR? (Has there also been any additional testing?)

• Related Python client changes (link commit/PR here)

• Related documentation changes (link commit/PR here)

• Other information:

• Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes/features)
• Docs have been added / updated (for bug fixes / features)