### Godot version

v4.0.beta17.mono.official [c40020513]

### System information

Windows 11 22H2

### Issue description

If a focused subwindow is destroyed, DisplayServerWindows may still attempt to send mouse motion events to that window, because `last_focused_window` isn't updated until another window is focused.

```
ERROR: Condition "!windows.has(p_window)" is true. Returning: Point2i()
   at: window_get_position (platform/windows/display_server_windows.cpp:999)
```

### Steps to reproduce

Run the MRP, click some non-Godot application window to focus it, then click the "CLOSE" button in the secondary window. This destroys the window without re-focusing the main window, so hovering the mouse over the main window will produce the error message above.

### Minimal reproduction project

[native_windows_hover.zip](https://github.com/godotengine/godot/files/10573386/native_windows_hover.zip)

_THREAD_SAFE_METHOD_
	switch (p_screen) {
		case SCREEN_PRIMARY: {
			p_screen = get_primary_screen();
		} break;
		case SCREEN_OF_MAIN_WINDOW: {
			p_screen = window_get_current_screen(MAIN_WINDOW_ID);
		} break;
		default:
			break;
	}
	EnumRefreshRateData data = { 0, p_screen, SCREEN_REFRESH_RATE_FALLBACK };
	EnumDisplayMonitors(nullptr, nullptr, _MonitorEnumProcRefreshRate, (LPARAM)&data);
	return data.rate;
}
void DisplayServerWindows::screen_set_keep_on(bool p_enable) {
	if (keep_screen_on == p_enable) {
		return;
	}
	if (p_enable) {
		const String reason = "Godot Engine running with display/window/energy_saving/keep_screen_on = true";
		Char16String reason_utf16 = reason.utf16();
		REASON_CONTEXT context;
		context.Version = POWER_REQUEST_CONTEXT_VERSION;
		context.Flags = POWER_REQUEST_CONTEXT_SIMPLE_STRING;
		context.Reason.SimpleReasonString = (LPWSTR)(reason_utf16.ptrw());
		power_request = PowerCreateRequest(&context);
		if (power_request == INVALID_HANDLE_VALUE) {
			print_error("Failed to enable screen_keep_on.");