but ok on back, preview and live

Caused by: org.ametys.plugins.repository.AmetysRepositoryException: Child path cannot be null, empty or absolute
at org.ametys.plugins.repository.jcr.TraversableAmetysObjectHelper.getChild(TraversableAmetysObjectHelper.java:80)
at org.ametys.plugins.repository.jcr.DefaultTraversableAmetysObjectFactory.getChild(DefaultTraversableAmetysObjectFactory.java:51)
at org.ametys.plugins.repository.jcr.DefaultTraversableAmetysObject.getChild(DefaultTraversableAmetysObject.java:61)
at org.ametys.web.repository.site.SiteManager.getSite(SiteManager.java:170)
at org.ametys.web.transformation.xslt.AmetysXSLTHelper.absoluteSkinContext(AmetysXSLTHelper.java:91)
at sun.reflect.GeneratedMethodAccessor55.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.xalan.extensions.ExtensionHandlerJavaClass.callFunction(ExtensionHandlerJavaClass.java:367)
... 113 more