Steps:
1) Open Monitoring -> Overview page and make sure you see some data or triggers there.
2) In Administration -> General set option "Dropdown first entry" to "none".
3) Open Monitoring -> Overview page again. At first nothing is displayed. Select a group. And nothing is displayed. Try to filter something, but nothing is displayed.

Reason:
Possibly broken in r45904. There is quite a difference. In 2.4 there is simple code

 if ($config['dropdown_first_entry']) { // display 

But in 2.2 there is more logic when data should be displayed:

if ($config['dropdown_first_entry'] || $this->data['pageFilter']->applicationsSelected || $this->data['pageFilter']->groupsSelected) { // display