A dataset has been defined without a name.

How to fix

Ensure that you have a name attribute defined for the each dataset element.

Problem example:

{
  "datasets": [
    {
       // Missing "name" property
      "type": "Pattern",
      "values": ["##"]
    }
  ]
}

Ensure that you have a name attribute defined for each dataset element.

{
  "datasets": [
    {
      "name": "PhoneNumbers",                  // Added name
      "type": "Pattern",
      "values": ["###-###-####"]
    }
  ]
}