Marti Raudsepp authored Oct 21, 2021 and Benjamin Berg committed Feb 10, 2022

Despite the debounce logic introduced in
60621b90, GSD kept warning me of the
battery level every time my Logitech K600 keyboard (via Unifying
receiver) disconnects/reconnects.

Added another condition: when battery level drops to
`UP_DEVICE_LEVEL_NONE`, the previous entry in the hash table would not
be overwritten. This avoids duplicated warnings when transitioning
NONE->LOW->NONE->LOW.