title: Relay Error when deleting: RelayMutationQuery: Invalid field name on fat query
body: <p>I'm running into an issue when I attempt to commit a deletion mutation. When I commit, I get the error <code>Uncaught Invariant Violation: RelayMutationQuery: Invalid field name on fat query, `company`.</code>. Viewing, creating and updating nodes all work. For some reason I just can't delete. It mentions the company field in the fatQuery, but the only field I have in the fat query is the deletedUserId I get back from the server. Thanks in advance!</p>
  
  <p>Component: </p>
  
  <pre><code>import React, {Component} from 'react';
  import Relay from 'react-relay';
  import {Link} from 'react-router';
  import DeleteUserMutation from 'mutations/DeleteUserMutation';
  import styles from './EmployeeItem.css';
  
  class EmployeeItem extends Component {
    render() {
      const {user} = this.props;
      return (
        &lt;div className={styles.employee}&gt;
          &lt;p&gt;&lt;strong&gt;ID:&lt;/strong&gt; {user.id}&lt;/p&gt;
          &lt;p&gt;&lt;strong&gt;First Name:&lt;/strong&gt; {user.firstName}&lt;/p&gt;
          &lt;p&gt;&lt;strong&gt;Last Name:&lt;/strong&gt; {user.lastName}&lt;/p&gt;
          &lt;p&gt;&lt;strong&gt;Email:&lt;/strong&gt; {user.email}&lt;/p&gt;
          &lt;div className="btn-group"&gt;
            &lt;Link to={`/company/employees/${user.id}`} className="btn btn-primary"&gt;View Employee&lt;/Link&gt;
            &lt;button onClick={this.handleRemove} className="btn btn-danger"&gt;Delete User&lt;/button&gt;
          &lt;/div&gt;
        &lt;/div&gt;
      )
    }
  
    handleRemove = (e) =&gt; {
      e.preventDefault();
      const {user, company} = this.props;
  
      Relay.Store.commitUpdate(new DeleteUserMutation({user, company}));
    };
  }
  
  export default Relay.createContainer(EmployeeItem, {
    fragments: {
      company: () =&gt; Relay.QL`
        fragment on Company {
          id
          ${DeleteUserMutation.getFragment('company')}
        }
      `,
      user: () =&gt; Relay.QL`
        fragment on User {
          id
          firstName
          lastName
          email
          ${DeleteUserMutation.getFragment('user')}
        }
      `
    }
  });
  </code></pre>
  
  <p>Mutation:</p>
  
  <pre><code>import React from 'react';
  import Relay from 'react-relay';
  
  export default class DeleteUserMutation extends Relay.Mutation {
    static fragments = {
      company: () =&gt; Relay.QL`
        fragment on Company {
          id
        }
      `,
      user: () =&gt; Relay.QL`
        fragment on User {
          id
        }
      `
    };
  
    getMutation() {
      return Relay.QL`mutation {deleteUser}`;
    }
  
    getFatQuery() {
      return Relay.QL`
        fragment on DeleteUserPayload {
          deletedUserId
        }
      `;
    }
  
    getVariables() {
      return {
        id: this.props.user.id,
      }
    }
  
    getConfigs() {
      return [{
        type: 'NODE_DELETE',
        parentName: 'company',
        parentID: this.props.company.id,
        connectionName: 'employees',
        deletedIDFieldName: 'deletedUserId'
      }]
    }
  
    // Wasn't sure if this was causing the error but it appears to be 
    // something else.
    // getOptimisticResponse() {
    //   return {
    //     deletedUserId: this.props.user.id
    //   }
    // }
  }
  </code></pre>