fix: allow empty communities in config (#104)

* fix: allow configuring empty v3 array

splunk_connect_for_snmp_traps/manager/trap_server.py

@@ -108,7 +108,7 @@ def setup_v3(self, snmp_config):
         user3: snmpv3test3
         sudo snmptrap -e 0x8000000004030203 -v3 -l noAuthNoPriv -u snmpv3test3 localhost:2162 123 1.3.6.1.6.3.1.1.5.1
         """
-        for user_config in snmp_config["communities"].get("v3", None):
+        for user_config in snmp_config["communities"].get("v3", []):
             # user_config = snmp_config["communities"]["v3"].get(user)
             logger.info(f"Configuring V3 {user_config}")
             username = user_config.get("userName", None)