Possible to disable touchpad when it's the only pointing device

Touchpad can be disabled when it's the only pointing device, rending the mouse inoperable. No warning dialog. I've accidentally clicked this button and needed to reenable it using tab to highlight the button and enter to 'click' it.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: unity-control-center 15.04.0+16.04.20160119-0ubuntu1
Uname: Linux 4.4.0-040400-generic x86_64
ApportVersion: 2.19.4-0ubuntu1
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Feb 4 22:22:15 2016
ExecutablePath: /usr/bin/unity-control-center
InstallationDate: Installed on 2015-12-24 (42 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Alpha amd64 (20151209)
ProcEnviron:
 PATH=(custom, user)
 SHELL=/bin/bash
 LANG=en_US.UTF-8
 LANGUAGE=en_US
 XDG_RUNTIME_DIR=<set>
SourcePackage: unity-control-center
UpgradeStatus: No upgrade log present (probably fresh install)