message: fix entity-source color showing black
  fixes
  now always using light-grey/white for regions with unkown source
diff: @@ -143,7 +143,9 @@ export function EntitySourceColorTheme(ctx: ThemeDataContext, props: PD.Values<E
  const seqToSrc = seqToSrcByModelEntity.get(mK);
  if (seqToSrc) {
  // minus 1 to convert seqId to array index
  - return palette.color(seqToSrc[StructureProperties.residue.label_seq_id(location) - 1] - 1);
  + const src = seqToSrc[StructureProperties.residue.label_seq_id(location) - 1] - 1;
  + // check for -1 as not all sequence ids have a src given
  + return src === -1 ? DefaultColor : palette.color(src);
  } else {
  return DefaultColor;
  }
  