Allow ns-op.detail to be None

Change-Id: I1af0d1aba38c5418f54bf6b9e6aa8ddfea1ea8bf
Signed-off-by: tierno <alfonso.tiernosepulveda@telefonica.com>
diff --git a/osmclient/scripts/osm.py b/osmclient/scripts/osm.py
index 1461760..62be7f7 100755
--- a/osmclient/scripts/osm.py
+++ b/osmclient/scripts/osm.py
@@ -731,7 +731,7 @@
                            wrap_text(text=detail,width=50)])
         else:
             table.add_row([op['id'], op['lcmOperationType'], action_name,
-                           op['operationState'], date, wrap_text(text=detail,width=50)])
+                           op['operationState'], date, wrap_text(text=detail or "",width=50)])
     table.align = 'l'
     print(table)