Not allowed in prolog grails XML error

I have the following on a Curl command:

  curl -i -H "Content-Type: text/xml" -d '<sample:WIB xmlns:sample="www.sample.com"><sample:Customer><sample:Catalog_ID>01</sample:Catalog_ID><sample:Shop_ID>01</sample:Shop_ID></sample:Customer></sample:WIB>' http://localhost:8080/app/API/

My Grails controller is:

  def index() {
    String xml = request.XML.toString();
    def workXml = new XmlSlurper().parseText(xml)
  }

I get the error when parsing I have also tried this:

 def workXml = new XmlSlurper().parseText(xml).declareNamespace(sample: 'sample')

I get the same error:

This is the stack trace:

 Message: Content is not allowed in prolog.
 Line | Method
->>   10 | index     in app.APIController$$EP3387M0
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  
|    198 | doFilter  in grails.plugin.cache.web.filter.PageFragmentCachingFilter
|     63 | doFilter  in grails.plugin.cache.web.filter.AbstractFilter
|     53 | doFilter  in grails.plugin.springsecurity.web.filter.GrailsAnonymousAuthenticationFilter
|     49 | doFilter  in grails.plugin.springsecurity.web.authentication.RequestHolderAuthenticationFilter
|     82 | doFilter  in grails.plugin.springsecurity.web.authentication.logout.MutableLogoutFilter
|   1145 | runWorker in java.util.concurrent.ThreadPoolExecutor
|    615 | run       in java.util.concurrent.ThreadPoolExecutor$Worker
^    745 | run . . . in java.lang.Thread

Any Ideas with this?