Cope better with possible VLAN setups

If we're not explicitly on a VLAN, it seems we're on 1. Don't pass an
empty string through the parser, just say [1]

Change-Id: I981b2994f1d8d930050dd164c71302daeb790233
diff --git a/drivers/NetgearXSM.py b/drivers/NetgearXSM.py
index 9a3c945..9a76208 100644
--- a/drivers/NetgearXSM.py
+++ b/drivers/NetgearXSM.py
@@ -658,9 +658,12 @@
                         vlan_text += (match.group(1))
                     else:
                         vlan_text = match.group(1)
-            
-            vlans = self._parse_vlan_list(vlan_text)
-            return vlans
+
+            if vlan_text is None:
+                return [1]
+            else:
+                vlans = self._parse_vlan_list(vlan_text)
+                return vlans
 
         except PExpectError:
             # recurse on error