message: fix applyMarkerAction edge case
diff: @@ -105,9 +105,14 @@ export function applyMarkerAction(array: Uint8Array, set: OrderedSet, action: Ma
  applyMarkerActionAtPosition(array, i, action);
  }
  + // to prevent applying "toggle" twice check for edge case where
  + // viewEnd <= viewStart, which resolves to the "front" and "back"
  + // intervals being the same range
  + if (frontStart !== backStart) {
  for (let i = backStart; i < backEnd; ++i) {
  applyMarkerActionAtPosition(array, i, action);
  }
  + }
  } else {
  switch (action) {
  case MarkerAction.Highlight:
  