gnome-shell: The polkitAgent: Hide authentication dialogs while locked commit causes issues when auth dialog is canceled
Affects all apps that call pkexec to authenicate, most apps don't crash but become 'unresponsive' & any subsequent attempts to use pkexec fail until gnome-shell is restarted. A test case & crash report for gnome-control-center > users > unlock > cancel is located here https://bugs.launchpad.net/ubuntu/+source/gnome-control-center/+bug/1765353
Simple test using software-properties-gtk:
Open software-properties-gtk, do something that requires auth like click on the sources button. In the pkexec popup click cancel.
The pop up will disappear but the s-p-gtk window cannot be closed. Either force quit or kill the s-p-gtk process, then try to open s-p-gtk again, it will not open. The process will be started but in a sleeping state..
Try to use any other app that uses a pkexec auth, the app will either not open or the the action that would normally pop up the pkexec auth dialogue will not work.
Only a restart, login/out or alt+F2 > r will restore ability to use pkexec again. Only a restart will remove any zombie processes, if any..