Geary doesn't display window buttons on the left side of the title bar

On Ubuntu 18.04.2, if you change the setting org.gnome.desktop.wm.preferences button-layout to 'close,minimize,maximize', window buttons should be displayed on the left side of the title bar. However, Geary 0.12.0-1ubuntu1 always displays them on the right side, no matter what your settings are.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: geary 0.12.0-1ubuntu1
ProcVersionSignature: Ubuntu 4.18.0-18.19~18.04.1-generic 4.18.20
Uname: Linux 4.18.0-18-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.9-0ubuntu7.6
Architecture: amd64
CurrentDesktop: GNOME
Date: Sun May 5 17:45:45 2019
InstallationDate: Installed on 2018-12-11 (145 days ago)
InstallationMedia: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
SourcePackage: geary
UpgradeStatus: No upgrade log present (probably fresh install)