Fix galleries with both artist and cosplayer tags

Legacy issue of E-Hentai's tag namespacing changes.

app/src/main/kotlin/com/hippo/ehviewer/EhDB.kt

@@ -150,7 +150,7 @@ object EhDB {
         if (artists.isNotEmpty()) {
             val dao = db.downloadArtistDao()
             dao.deleteByGid(gid)
-            dao.insert(artists)
+            dao.insertOrIgnore(artists)
         }
     }
 

app/src/main/kotlin/com/hippo/ehviewer/dao/DownloadArtistDao.kt

@@ -2,12 +2,13 @@ package com.hippo.ehviewer.dao
 
 import androidx.room.Dao
 import androidx.room.Insert
+import androidx.room.OnConflictStrategy
 import androidx.room.Query
 
 @Dao
 interface DownloadArtistDao {
-    @Insert
-    suspend fun insert(downloadArtists: List<DownloadArtist>)
+    @Insert(onConflict = OnConflictStrategy.IGNORE)
+    suspend fun insertOrIgnore(downloadArtists: List<DownloadArtist>)
 
     @Query("DELETE FROM DOWNLOAD_ARTISTS WHERE GID = :gid")
     suspend fun deleteByGid(gid: Long)