Error: Invalid or incomplete introspection result. Ensure that you are passing "data" property of introspection response and no "errors" was returned alongside: null.

**Intended outcome:**

I can use apollo VS code extension without errors

**Actual outcome:**

I get the following error from the extension:

> Error: Invalid or incomplete introspection result. Ensure that you are passing "data" property of introspection response and no "errors" was returned alongside: null.

**How to reproduce the issue:**

My config file is like this:

```
module.exports = {
client: {
service: {
name: 'API GraphQl',
service: 'service-name@master'
}
}
}
```
The master variant exists and has been recently updated.

**Versions**

`"apollo": "^2.31.0",`

Start with the Apollo VS Code extension and the shown client.service configuration, then reproduce the failure using the existing master variant and inspect the introspection response. Done means the extension accepts the service response and no longer reports an invalid or incomplete introspection result.

Written by the indexing model from the issue text.