[fix] with-apollo: Cannot read property 'data' (#3226)

* [fix] with-apollo: Cannot read property 'data'

When we create the initial serverState, we need to create the
 eventual construct of the Apollo Data to reside within

Later in the constructor this allows for the initApollo to either
 be generated from SSR, or to init from scratch.

Fixes
> Cannot read property 'data' of undefined
> TypeError: Cannot read property 'data' of undefined

* [refactor] with-apollo: reduce init `serverState`

No need to explicitly set `data` as empty.
This trims up 4 lines. 😀️

examples/with-apollo/lib/withData.js

@@ -17,7 +17,8 @@ export default ComposedComponent => {
     }
 
     static async getInitialProps (ctx) {
-      let serverState = {}
+      // Initial serverState with apollo (empty)
+      let serverState = { apollo: { } }
 
       // Evaluate the composed component's getInitialProps()
       let composedInitialProps = {}