PUT endpoint for upenn_contrast/multiple seems buggy

[arjunrajlab]

I tried using the web API with a few different JSON inputs and it gave internal server errors. For instance:

[
  {
    "_id": "66ec79a643c86080ec9043b1",
    "color": "#FF00FF",
    "datasetId": "66b111fa8e2b55905fadb2e0"
  }
]

didn't work, saying internal server error. I tried also adding an "id" field with the same ID string, and it returned with success, but it didn't actually seem to do anything.