Fix maintenance mode
Fix maintenance mode

When the server is in maintenance mode, apps are not loaded.
That means apps/theming/ is not in the allowed paths. So we
need to check without autoloading, whether the class exists.

endsguy/server,michaelletzgus/nextcloud-server,jbicha/server,jbicha/server,endsguy/server,pmattern/server,nextcloud/server,jbicha/server,whitekiba/server,pixelipo/server,andreas-p/nextcloud-server,whitekiba/server,Ardinis/server,xx621998xx/server,xx621998xx/server,michaelletzgus/nextcloud-server,nextcloud/server,whitekiba/server,Ardinis/server,michaelletzgus/nextcloud-server,pmattern/server,andreas-p/nextcloud-server,andreas-p/nextcloud-server,endsguy/server,pmattern/server,endsguy/server,pixelipo/server,pixelipo/server,xx621998xx/server,whitekiba/server,pixelipo/server,Ardinis/server,endsguy/server,jbicha/server,andreas-p/nextcloud-server,Ardinis/server,xx621998xx/server,michaelletzgus/nextcloud-server,Ardinis/server,pixelipo/server,andreas-p/nextcloud-server,nextcloud/server,pmattern/server,pmattern/server,whitekiba/server,xx621998xx/server,jbicha/server,nextcloud/server