XMLDialog.nas: improve warning message
In my tests, me.name and node.location() seem to be nil or empty.
me.dialog.name and node.getPath() appear to give the desired
information. This changes warnings from
XML GUI: config property 'label' of '' is not marked for translation.
to, for instance,
XML GUI: config property
/group[1]/group[1]/checkbox[3]/labelof 'view' dialog is not marked for translation.