fix(user-management): Fix deleting user in hidden group(s)

E.g. guest_users

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

apps/settings/src/store/users.js

@@ -184,6 +184,10 @@ const mutations = {
 				state.userCount-- // decrement Active Users count
 				user.groups.forEach(userGroup => {
 					const group = state.groups.find(groupSearch => groupSearch.id === userGroup)
+					if (!group) {
+						console.warn('User group ' + userGroup + ' does not exist during user removal')
+						return
+					}
 					group.usercount-- // decrement group total count
 				})
 			} else {