PerKeyLighting.write_key_value dereferenced self._value without the
initialization guard that the base Settings.write_key_value has. On a
fresh CLI invocation (solaar config <dev> per-key-lighting <key> <color>)
nothing has read the setting yet, so _value is still None and the write
crashes with 'NoneType' object does not support item assignment.
The GUI never hits this because it reads all settings on attach.
Initialize via read(), which for this write-only 0x8081 setting loads
the persisted map or fabricates the all-"No change" sentinel map.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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