Keyboard input doesn't work in UnitMainLoop when Idle function is registered

[AaronLieberman]

Describe the bug
Keyboard input doesn't work in UnitMainLoop when Idle function is registered.

To Reproduce
Run this application on Linux:

using Terminal.Gui;

Application.Init();
Application.Top.Add(new TextField { Width = 30, Height = 1 });

// comment out this line and it works on Linux (but no idle function, of course)
Application.MainLoop.AddIdle(() => true);

Application.Run();
Application.Shutdown();

Expected behavior
Text field is editable. Ctrl+Q quits app. If you comment out the AddIdle line

Desktop (please complete the following information):

• This same code runs fine on Windows 11 native
• It doesn't work on Linux. Tested on native Ubuntu 20.04 and Windows 11 WSL2 Ubuntu 20.04.