Removing all Default Handlers in the Applications tab prevents resetting
The bug was reported on https://bugs.launchpad.net/ubuntu/+source/gnome-control-center/+bug/1817427
Package: gnome-control-center 1:3.31.90-1ubuntu3
'When I remove all the Default Handlers of an application in gnome-control-center, I am unable to reset the default handlers to the original values as the reset button is gone.
I expect the reset button to still be there, so that I can recover the removed Default Handlers when I need to.'