Return empty array instead of undefined in mapTimestampToAxisTicksByFormat

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/module/timeLabel.js

@@ -251,4 +251,5 @@ export const mapTimestampToAxisTicksByFormat = (timeStampArr, timeFormat) => {
   if (timeStampArr) {
     return timeStampArr.map((ts) => moment(ts).format(timeFormat));
   }
+  return [];
 };