Steps to reproduce:

• send maintenance.create API call through JSON RPC

  {"jsonrpc":"2.0","method":"maintenance.create","params":{"name":"M1","active_since":"1514757600","active_till":"1546207200","groupids":["2"],"timeperiods":[{"every":1,"dayofweek":64,"start_time":3600,"period":7200}]},"id":0,"auth":"56467b66a9e0630f7b574393493c6c5d"}

Result

Undefined index: userid [api_jsonrpc.php:63 -> CJsonRpc->execute() -> CLocalApiClient->callMethod() -> call_user_func_array() -> CMaintenance->create() -> add_audit_details() -> CConfigFile->{closure}() in include/audit.inc.php:154]