fix(creator-channel): 빈 연재 요일 문구를 보완한다

src/main/kotlin/kr/co/vividnext/sodalive/v2/creator/channel/series/domain/CreatorChannelSeriesQueryPolicy.kt

@@ -35,6 +35,9 @@ class CreatorChannelSeriesQueryPolicy {
     }
 
     fun publishedDaysOfWeekText(days: Set<SeriesPublishedDaysOfWeek>, locale: String): String {
+        if (days.isEmpty()) {
+            return randomText(locale)
+        }
         if (days.contains(SeriesPublishedDaysOfWeek.RANDOM)) {
             return randomText(locale)
         }