Internal Server Error when nullable input not provided to federated graph.

[Collin3]

I was converting a graph that we used to hit directly over to be a federated service and some of our acceptance tests bombed out with the following error

{
  "errors": [
    {
      "message":"Cannot convert undefined or null to object",
      "extensions": {
        "code": "INTERNAL_SERVER_ERROR",
        "exception": {
          "stacktrace": [
            "TypeError: Cannot convert undefined or null to object",
            "    at hasOwnProperty (<anonymous>)",
            "    at hasOwnProperty (/app/node_modules/graphql/execution/values.js:219:42)",
            "    at _loop (/app/node_modules/graphql/execution/values.js:86:10)",
            "    at coerceVariableValues (/app/node_modules/graphql/execution/values.js:119:16)",
            "    at Object.getVariableValues (/app/node_modules/graphql/execution/values.js:48:19)",
            "    at ApolloGateway.validateIncomingRequest (/app/node_modules/@apollo/gateway/dist/index.js:365:37)",
            "    at ApolloGateway.<anonymous> (/app/node_modules/@apollo/gateway/dist/index.js:75:43)",
            "    at Generator.next (<anonymous>)",
            "    at /app/node_modules/@apollo/gateway/dist/index.js:8:71",
            "    at new Promise (<anonymous>)"
          ],
        },
      },
      "code": "INTERNAL_SERVER_ERROR",
      "exception": {
        "stacktrace": [
          "TypeError: Cannot convert undefined or null to object",
          "    at hasOwnProperty (<anonymous>)",
          "    at hasOwnProperty (/app/node_modules/graphql/execution/values.js:219:42)",
          "    at _loop (/app/node_modules/graphql/execution/values.js:86:10)",
          "    at coerceVariableValues (/app/node_modules/graphql/execution/values.js:119:16)",
          "    at Object.getVariableValues (/app/node_modules/graphql/execution/values.js:48:19)",
          "    at ApolloGateway.validateIncomingRequest (/app/node_modules/@apollo/gateway/dist/index.js:365:37)",
          "    at ApolloGateway.<anonymous> (/app/node_modules/@apollo/gateway/dist/index.js:75:43)",
          "    at Generator.next (<anonymous>)","    at /app/node_modules/@apollo/gateway/dist/index.js:8:71",
          "    at new Promise (<anonymous>)"
        ],
      },
    }
  ]
}

After some debugging I found that it was because our acceptance test was reusing a query (similar to below)

query GetProducts($storeId: String) {
  products(storeId: $storeId) {
    productId
    name
 }
}

And in one test it would pass in a storeId and in another test it would not pass in any input variables. When not providing an input variable, the query would error out, but if we provided a variable of type String, null, or undefined, the query would work. It seemed odd that this would error out when going through the federated gateway, but would work when hitting our federated service directly. Is this expected to error out? It seemed like a rather confusing error message if it is expected to not work.

Our federated gateway is running @apollo/federation@0.14.1, @apollo/gateway@0.14.1andapollo-server@2.12.0Our federated service is currently runningapollo-server-hapi@2.8.1`