message: Fix out of bounds error in easymotion dimming logic
  Fixes
diff: @@ -360,7 +360,7 @@ export class EasyMotion implements IEasyMotion {
  });
  } else {
  const prevMarker = markers[markers.indexOf(marker) - 1];
  - const prevKeystroke = prevMarker.name.substr(this.accumulation.length);
  + const prevKeystroke = prevMarker.name.substring(this.accumulation.length);
  const prevDimPos = prevMarker.position;
  const offsetPrevDimPos = prevDimPos.withColumn(
  prevDimPos.character + prevKeystroke.length
  @@ -389,9 +389,9 @@ export class EasyMotion implements IEasyMotion {
  }
  // for the last marker dim till document end
  - if (configuration.easymotionDimBackground) {
  + if (configuration.easymotionDimBackground && markers.length > 0) {
  const prevMarker = markers[markers.length - 1];
  - const prevKeystroke = prevMarker.name.substr(this.accumulation.length);
  + const prevKeystroke = prevMarker.name.substring(this.accumulation.length);
  const prevDimPos = dimmingZones[dimmingZones.length - 1].range.end;
  const offsetPrevDimPos = prevDimPos.withColumn(prevDimPos.character + prevKeystroke.length);
  