Desktop Dock is invisible after relogin

[Oliver Granseier]

# Reproduction Instructions
 1. Lock screen by pressing WIN+L
 2. Relogin to Ubuntu Desktop

# Current result
The application dock is invisible.

# Expected result
The application dock is visible.

HINT: I have 3 screens connected and moved the dock to the second screen.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-desktop 1.417
ProcVersionSignature: Ubuntu 4.15.0-36.39-generic 4.15.18
Uname: Linux 4.15.0-36-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.9-0ubuntu7.4
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Thu Oct 25 11:33:47 2018
InstallationDate: Installed on 2018-10-19 (6 days ago)
InstallationMedia: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-meta
UpgradeStatus: No upgrade log present (probably fresh install)