"Lock to Launcher" generates invalid .desktop file when path contains spaces

[niedzielski]

Unity v7.5.0+16.10.20160906.1-0ubuntu1
Ubuntu v16.10

Repro steps:
1. Open an app with spaces in the executable path that has no .desktop file
2. Right click the app icon in the launcher and click "Lock to Launcher"

Expected results:
A valid .desktop file is generated

Actual results:
A file like the following is generated in ~/.local/share/applications:
[Desktop Entry]
Encoding=UTF-8
Version=1.0
Type=Application
Name=Salvage Solitude 8140 Configuration
Icon=salvagesolitude8140v0_6_x86_64.png
Path=/home/stephen/.config/itch/apps/Salvage Solitude 8140/SalvageSolitude8140v0.6 - Linux
Exec=/home/stephen/.config/itch/apps/Salvage Solitude 8140/SalvageSolitude8140v0.6 - Linux/SalvageSolitude8140v0.6.x86_64
StartupNotify=false
StartupWMClass=SalvageSolitude8140v0.6.x86_64
OnlyShowIn=Unity;
X-UnityGenerated=true

The spaces should be escaped or the locked app will disappear on the subsequent session