Uncaught TypeError: Cannot read property 'getAttribute' of undefined
    at Object.response (jsf.js.xhtml?ln=javax.faces&stage=Development:2814)
    at Object.onComplete (jsf.js.xhtml?ln=javax.faces&stage=Development:1779)
    at FrameTransport.AjaxEngine.req.xmlReq.onreadystatechange (jsf.js.xhtml?ln=javax.faces&stage=Development:1760)
    at FrameTransport.callback (jsf.js.xhtml?ln=javax.faces&stage=Development:367)
    at HTMLIFrameElement.<anonymous> (jsf.js.xhtml?ln=javax.faces&stage=Development:400)

<h:inputFile value="#{imagemPerfil.arquivo}" required="true" >

            </h:inputFile>
            <h:commandButton
                class="btn btn-primary" value="Salvar" action="#{imagemPerfil.handleFileUpload()}">

                <f:ajax execute="@form" render="@form" />

            </h:commandButton>

        </h:form>

/**
 *
 */
private static final long serialVersionUID = 3131478679593318664L;
private Part arquivo;
private UploadedFile uploadFile;

public Part getArquivo() {
    return arquivo;
}

public void setArquivo(Part arquivo) {
    this.arquivo = arquivo;
}


public UploadedFile getUploadFile() {
    return uploadFile;
}

public void setUploadFile(UploadedFile uploadFile) {
    this.uploadFile = uploadFile;
}

public MudarImagemPerfil() {

}

public void handleFileUpload() {

    if(arquivo != null) {
        System.out.println("file size: " + arquivo.getSize());
        System.out.println("file type: " + arquivo.getContentType());
    }else {
        System.out.println("Arquivo está nulo");
    }

}