Server can "softlock" client

This bug is caused by the fix of MC-58961.

When the server kicks the client with a very long kick message, the back button can be pushed offscreen. If it is long enough, you can make the button unreachable even after resizing the window.

On certain GUI scales, the limit of the vanilla console input is just enough to "softlock" the game (though a window resize will fix it). If the server is modded, the kick message can simply be filled with newlines to make the screen impossible to escape.

This can be fixed either by never allowing the button to be off-screen (in which case it would sometimes overlap the text), or by letting the user scroll through the kick message and placing the button in a fixed spot.