Fix for issue 528 (#529)

Author: mikewiebe

roles/validate/files/rules/ibgp_vxlan/310_topology_switch_interface_breakouts.py

@@ -10,6 +10,8 @@ def match(cls, inventory):
 
         # Extract switches from the inventory
         switches = inventory.get("vxlan", {}).get("topology", {}).get("switches", [])
+        if switches is None:
+            return results
 
         # Process each switch
         for switch in switches: