occ groupquota:list with a group which has been deleted results in an exception

I'm fairly certain that this is because I have a group which I have since set a group quota for and then deleted.

root@cloud:~# ./occ groupquota:list
/usr/share/nginx/nextcloud ~
PHP Warning:  JIT is incompatible with third party extensions that override zend_execute_ex(). JIT disabled. in Unknown on line 0
group                                         |free                                           |used                                           |total                                          
----------------------------------------------|-----------------------------------------------|-----------------------------------------------|-----------------------------------------------
Bollinger                                     |2198996259191                                  |26996361                                       |2199023255552                                  
Brown                                         |2199023255552                                  |0                                              |2199023255552                                  
Dumbass                                       |1311362628688                                  |887660626864                                   |2199023255552                                  
An unhandled exception has been thrown:
TypeError: OCA\GroupQuota\Quota\UsedSpaceCalculator::getUsedSpaceByGroup(): Argument #1 ($group) must be of type OCP\IGroup, null given, called in /usr/share/nginx/nextcloud/apps/groupquota/lib/Command/QuotaList.php on line 78 and defined in /usr/share/nginx/nextcloud/apps/groupquota/lib/Quota/UsedSpaceCalculator.php:42
Stack trace:
#0 /usr/share/nginx/nextcloud/apps/groupquota/lib/Command/QuotaList.php(78): OCA\GroupQuota\Quota\UsedSpaceCalculator->getUsedSpaceByGroup()
#1 /usr/share/nginx/nextcloud/3rdparty/symfony/console/Command/Command.php(326): OCA\GroupQuota\Command\QuotaList->execute()
#2 /usr/share/nginx/nextcloud/core/Command/Base.php(161): Symfony\Component\Console\Command\Command->run()
#3 /usr/share/nginx/nextcloud/3rdparty/symfony/console/Application.php(1078): OC\Core\Command\Base->run()
#4 /usr/share/nginx/nextcloud/3rdparty/symfony/console/Application.php(324): Symfony\Component\Console\Application->doRunCommand()
#5 /usr/share/nginx/nextcloud/3rdparty/symfony/console/Application.php(175): Symfony\Component\Console\Application->doRun()
#6 /usr/share/nginx/nextcloud/lib/private/Console/Application.php(183): Symfony\Component\Console\Application->run()
#7 /usr/share/nginx/nextcloud/console.php(87): OC\Console\Application->run()
#8 /usr/share/nginx/nextcloud/occ(33): require_once('...')
#9 {main}~

I'm pretty sure, but not postive that the way to reproduce this is:

1. Make a group
2. set a quota on that group
3. delete said group

There might also be some crufty values in the database as well since I was an early adopter of the plugin. However, in either case, there needs to be a fall back if getting a group returns None.. IE, that group no longer exists.

Start with apps/groupquota/lib/Command/QuotaList.php at line 78 and apps/groupquota/lib/Quota/UsedSpaceCalculator.php at line 42, then reproduce the issue with occ groupquota:list after deleting a group that has a quota. Done means the command handles the deleted group without throwing the shown TypeError and still reports the remaining quota entries.