Clicking the `Install' button in muon-discover has no discernable effect

[rww]

Steps to reproduce:

1) Click the Application Launcher in the bottom left of the screen
2) Type `Muon' and click on `Muon Discover'
3) When Muon opens, click the Search box and type Chromium (which I don't have installed)
4) Click the `Install' button next to `Chromium Web Browser'
5) Nothing happens. No feedback to say it's doing anything, and as far as I can tell it is in fact not doing anything.

This is on a brand new Kubuntu vivid install from daily.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: muon-discover 4:5.2.0-0ubuntu2
ProcVersionSignature: Ubuntu 3.18.0-13.14-generic 3.18.5
Uname: Linux 3.18.0-13-generic x86_64
ApportVersion: 2.16.1-0ubuntu2
Architecture: amd64
CurrentDesktop: KDE
Date: Sun Feb 15 18:49:16 2015
InstallationDate: Installed on 2015-02-16 (0 days ago)
InstallationMedia: Kubuntu 15.04 "Vivid Vervet" - Alpha amd64 (20150215)
SourcePackage: muon
UpgradeStatus: No upgrade log present (probably fresh install)