* File.readbytesuntil does not terminate strings. So the string buffer needs to be filled with zero's before reading.
* fix crashes (mem corruption) when ledmap file has too many / too few entries.
* initialize unused map places with "identity" (same led) mapping
before fix:
> Reading LED map from /ledmap1.json
> ("width": 60edmap1.json) ("height": 90edmap1.json)
> resetSegments 1 60x90
> allocLeds (0,0 to 60,90), 16200 from 0
> allocLeds (0,0 to 60,90), 16200 from 6
> deserializeMap 60 x 90 customMappingTable alloc 5400 from 0
after:
> Reading LED map from /ledmap1.json
> ("width": 60) ("height": 9)
> resetSegments 1 60x9
> allocLeds (0,0 to 60,9), 1620 from 0
> allocLeds (0,0 to 60,9), 1620 from 6
> deserializeMap 60 x 9
> deserializemap customMappingTable alloc 540 from 0
86b0eeafb7