adding external port to SDN-Assist when connected to WIM

Change-Id: Ic6902950915a8fde50d162cf425c1851e5bc001c
Signed-off-by: tierno <alfonso.tiernosepulveda@telefonica.com>
diff --git a/osm_ro/utils.py b/osm_ro/utils.py
index 2afbc85..1e3a8ee 100644
--- a/osm_ro/utils.py
+++ b/osm_ro/utils.py
@@ -225,6 +225,8 @@
     :param text:
     :return:
     """
+    if text is None:
+        return (None, )
     start = text.find("[")
     end = text.find("]")
     if start < 0 or end < 0: