Launchpad webapp sometimes is shown two times

Launchpad webapp, sometimes, is shown two times in the unity left panel. (see attached screenshot)

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: unity-webapps-launchpad 2.2
ProcVersionSignature: Ubuntu 3.8.0-19.29-generic 3.8.8
Uname: Linux 3.8.0-19-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.9.2-0ubuntu8
Architecture: amd64
Date: Sat Apr 27 10:18:07 2013
InstallationDate: Installed on 2013-04-25 (1 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=it_IT.UTF-8
 SHELL=/bin/bash
SourcePackage: unity-webapps-launchpad
UpgradeStatus: No upgrade log present (probably fresh install)