Check whether interface-list exits before querying its length

monitoring/zabbix_host.py

@@ -289,6 +289,8 @@ class Host(object):
     # check the exist_interfaces whether it equals the interfaces or not
     def check_interface_properties(self, exist_interface_list, interfaces):
         interfaces_port_list = []
+
+        if interfaces is not None:
             if len(interfaces) >= 1:
                 for interface in interfaces:
                     interfaces_port_list.append(int(interface['port']))