fix potential attribute error

diff --git a/sfa/util/xrn.py b/sfa/util/xrn.py
index f2ab48b..02f4adb 100644 (file)
--- a/sfa/util/xrn.py
+++ b/sfa/util/xrn.py
@@ -251,7 +251,7 @@ class Xrn:
         else:\r
             urn = "+".join(['',authority_string,self.type,Xrn.unescape(name)])\r
 \r
-        if self.id:\r
+        if hasattr(self, 'id') and self.id:\r
             urn = "%s:%s" % (urn, self.id)        \r
 \r
         self.urn = Xrn.URN_PREFIX + urn\r