### 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)

String id = "SYSTEM\\CurrentControlSet\\Control\\Keyboard Layouts\\" + String::num_int64((int64_t)p_layout, 16, false).lpad(8, "0");
	String ret;
	HKEY hkey;
	WCHAR layout_text[1024];
	memset(layout_text, 0, 1024 * sizeof(WCHAR));
	if (RegOpenKeyExW(HKEY_LOCAL_MACHINE, (LPCWSTR)(id.utf16().get_data()), 0, KEY_QUERY_VALUE, &hkey) != ERROR_SUCCESS) {
		return ret;
	}
	DWORD buffer = 1024;
	DWORD vtype = REG_SZ;
	if (RegQueryValueExW(hkey, L"Layout Text", nullptr, &vtype, (LPBYTE)layout_text, &buffer) == ERROR_SUCCESS) {
		ret = String::utf16((const char16_t *)layout_text);
	}
	RegCloseKey(hkey);
	return ret;
}
String DisplayServerWindows::keyboard_get_layout_name(int p_index) const {