Somebody help me with this error: "ApolloError.js: 43 Uncaught (in promise) Error: Network error: Can not read property 'Mutation' of undefined"

Hi, I am testing this from the local state with apollo client and it gives me this error when invoking the mutate method.

ApolloError.js: 43 Uncaught (in promise) Error: Network error: Can not read property 'Mutation' of undefined

---------- Code:

-------- updatePagPrincipal.js

import gql from 'graphql-tag';

export default gql'
mutation updatePagPrinc($index: String! , $value: String!) {
    updatePagPrinc(index: $index, value: $value) @client {
        bienvenido
        descripcion
    }
}
'

------ FormLogin.js

import React, {Fragment}from 'react'
import { compose, graphql  } from 'react-apollo';
import updatePagPrincipal from '../../LocalState/graphql/updatePagPrincipal'

class FormLogin extends React.Component{
constructor(props) {
    super(props);
    // create a ref to store the textInput DOM element
    this.titleInput = React.createRef();
    this.descriptionInput = React.createRef(); 

  }
render(){
    const { updatePagPrinc } = this.props 
    return (

             <Fragment>
             <form onSubmit={e => {
                     e.preventDefault();
                     updatePagPrinc({
                         variables: {
                         index: 'Titulo',
                         value: this.titleInput.current.value
                     }
                 })
                     console.log(this.titleInput.current.value)
                     this.titleInput.current.value = ""
                 }}>
                 <label> Titulo:</label><input type="Text" ref= 
         {this.titleInput}/>
                 {/* <label> descripcion:</label><input type="Text" ref= 
        {this.descriptionInput}/> */}
                 <button type="submit" >Guardar</button>
             </form>
         </Fragment>

    )
}
}

export default compose(graphql(updatePagPrincipal, {
name: 'updatePagPrinc'
}))(FormLogin);

----- index.js (Fragment of code)

............

const defaulState = {
pagPrincipal: {
__typename: 'PagPrincipal',
bienvenido: 'Bienvenido Hello!! estamos desde el local state',
descripcion: 'Este es el primer software web con tecnologia React, 
ApolloGraphQl, Material-ui, node.js y mongoDB'
},
datosNumericos: {
__typename: 'DatosNumericos',
cantStock: 0
}
}

 const stateLink = withClientState({
 cache,
 defaults: defaulState,

 resolver: {
 Mutation: {
  updatePagPrinc: (_, { index, value }, { cache }) => {
    console.log(index, value)
  }
  } 
  }
 })


 //Inicializando el ClienteApollo
 const client = new ApolloClient({
 //Unificando mi stado con el servidor
 link: ApolloLink.from([
  stateLink, //Unica Fuente de la verdad
  httpLink //Servidor ApolloGraphQl
 ]),
 cache
 });