title: graphql mutation using input object
body: <p>I'm using graphql apollo client for Android. I'm able to pass data using mutation for a single fields without any issue. While using input object in mutation the error <strong>cannot read property of email undefined</strong> occurred. But same graphql working while running in the browser. </p>
  
  <p>Graphql mutation</p>
  
  <pre><code>mutation signup($SignupInput:SignupInput) {
      signup(data: $SignupInput) {
          result{token,firstName,lastName,profileImage}
     }
  }
  </code></pre>
  
  <p>Input</p>
  
  <pre><code>    {"SignupInput": {"firstName": "John","lastName": "Peter","email": "john@gmail.com"
  ,"password": "123123"}}
  </code></pre>
  
  <p>Java Code for API call </p>
  
  <pre><code>final SignupInput signupInput=SignupInput.builder()
                  .firstName(edtSignUpName.getText().toString())
                  .lastName(edtSignUpLastName.getText().toString())
                  .email(actvSignUpEmail.getText().toString())
                  .password(edtSignUpPassword.getText().toString())
                  .profileImage("dasfasdfasdf.png").build();
  
  
          final SignupMutation signupMutation = SignupMutation.builder()
                  .signupInput(signupInput)
                  .build();
          signupCall = appController.apolloClient()
                  .mutate(signupMutation);
          signupCall.enqueue(dataCallback);
  </code></pre>