lightdm crashes when trying to switch keyboard layout

Steps to reproduce:

1. Have at least two keyboard layouts configured (i.e. English and Russian)
2. Configure hotkey to switch layouts (Settings -> Text Entry -> Switch to next source using:)
3. Lock desktop (Ctrl+Alt+L)
4. Press layout switch hotkey

After few seconds lightdm will crash, you will see desktop unlocked for a moment and then it will be locked again. After unlocking desktop an error report will show up.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: lightdm 1.18.2-0ubuntu2
Uname: Linux 4.7.0-040700-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: Unity
Date: Tue Aug 9 04:29:49 2016
EcryptfsInUse: Yes
InstallationDate: Installed on 2016-05-01 (100 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
SourcePackage: lightdm
UpgradeStatus: No upgrade log present (probably fresh install)