t: xmlui: fix handling unknown device
t: xmlui: fix handling unknown device

The branch else has never been executed and thus there was a hidden
bug. It does not show the unknown device XML element's contents
properly during testing.

Fixes: d67474b9798a ("t: xmlui: test basic operations of namespace device")
Fixes: 8d298d729c3b ("t: xmlui: assure the devices contain modules")
Signed-off-by: Jan Viktorin <3eab6ac54c005c4408f608556a6663b7f2abede7@fit.vutbr.cz>

BeeeOn/server,BeeeOn/server,BeeeOn/server,BeeeOn/server