Steps to reproduce:

• send API call through JSON RPC

  {
      "jsonrpc": "2.0",
      "method": "user.login",
      "params": {
          "user": "Admin",
          "password": "zabbix"
      },
      "id": 1
  }
  

Result:

Undefined index: auth [api_jsonrpc.php:63 -> CJsonRpc->execute() -> CConfigFile->{closure}() in include/classes/core/CJsonRpc.php:87]

Expected:
Code must be executed without PHP errors