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)
         }

src/test/kotlin/kr/co/vividnext/sodalive/v2/creator/channel/series/domain/CreatorChannelSeriesQueryPolicyTest.kt

@@ -71,6 +71,14 @@ class CreatorChannelSeriesQueryPolicyTest {
         assertEquals("ランダム", policy.publishedDaysOfWeekText(days, "ja"))
     }
 
+    @Test
+    @DisplayName("시리즈 탭 연재 요일은 비어 있으면 locale별 랜덤 문구로 fallback한다")
+    fun shouldReturnRandomTextWhenDaysAreEmpty() {
+        assertEquals("랜덤", policy.publishedDaysOfWeekText(emptySet(), "ko"))
+        assertEquals("Random", policy.publishedDaysOfWeekText(emptySet(), "en"))
+        assertEquals("ランダム", policy.publishedDaysOfWeekText(emptySet(), "ja"))
+    }
+
     @Test
     @DisplayName("시리즈 탭 연재 요일은 7개 요일이면 locale별 매일 문구를 반환한다")
     fun shouldReturnEveryDayTextWhenDaysContainAllWeekdays() {