/usr/share/gdm/greeter/applications/mime-dummy-handler.desktop is in gdm3 3.14.1-7.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 | [Desktop Entry]
Type=Application
Name=Dummy URI Handler
Exec=/bin/true %U
Terminal=false
StartupNotify=false
|