ETHREEOH-957: The delete preference webscript seems to not do anything

git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@17189 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/repo/preference/PreferenceServiceImpl.java

@@ -132,6 +132,7 @@ public class PreferenceServiceImpl implements PreferenceService
     /**
      * @see org.alfresco.repo.person.PersonService#getPreferences(java.lang.String, java.lang.String)
      */
+    @SuppressWarnings("unchecked")
     public Map<String, Serializable> getPreferences(String userName, String preferenceFilter)
     {
         Map<String, Serializable> preferences = new HashMap<String, Serializable>(20);