Bug #1241 : getTruncatedLabel always return non-empty string

pboard/pboard/model/data.py

     if liMaxLength>0 and len(lsTruncatedLabel)>liMaxLength:
       lsTruncatedLabel = lsTruncatedLabel[0:liMaxLength-1]+'…'
 
+    if lsTruncatedLabel=='':
+        lsTruncatedLabel = _('Titleless Document')
+
     return lsTruncatedLabel
 
   def getTruncatedContentAsText(self, piCharNb):