Microphone icon showing without sound input device connected

What happens: I do not have a microphone connected but the microphone volume bar is always shown when clicking on the speaker icon in the system indicator area on the top bar. The mixer does not show any sound input devices.

What I expect: If I do not have a sound input device connected to my computer there should be no volume bar to control its volume.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: indicator-sound 12.10.2+16.04.20160406-0ubuntu1
ProcVersionSignature: Ubuntu 4.8.0-36.36~16.04.1-generic 4.8.11
Uname: Linux 4.8.0-36-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.5
Architecture: amd64
CurrentDesktop: Unity
Date: Sun Feb 19 11:09:30 2017
InstallationDate: Installed on 2016-12-29 (51 days ago)
InstallationMedia: Ubuntu 14.04.5 LTS "Trusty Tahr" - Release amd64 (20160803)
ProcEnviron:
 LANGUAGE=de_DE
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: indicator-sound
UpgradeStatus: Upgraded to xenial on 2016-12-30 (50 days ago)