[-] WS : Fix bug #PSCFV-11328 : Don't insert attribute image(s) id if no id to insert

There was an issue with the webservice where inserting an empty <images node_type="image"></images> tag would result in an error 500 when it was not needed.
Merge pull request #1148 from adastier/patch-1

[-] WS : Fix bug #PSCFV-11328 : Don't insert attribute image(s) id if no...