add placeholder for when energy kcm is empty

currently when the system has no batteries, it will also have no history and it will never have wakeups because of https://gitlab.freedesktop.org/upower/upower/-/issues/69

all things put together it's very likely that a desktop system will not have any data in any of the models. when that happens show a placeholder message instead of an empty kcm

bump kirigami dep to get access to placeholdermessage