musikr: add empty library check

app/src/main/java/org/oxycblt/auxio/home/HomeGenerator.kt

@@ -149,7 +149,7 @@ private class HomeGeneratorImpl(
     }
 
     override fun empty() =
-        musicRepository.library == null
+        musicRepository.library?.empty() ?: true
 
     override fun songs() =
         musicRepository.library?.let { listSettings.songSort.songs(it.songs) } ?: emptyList()

musikr/src/main/java/org/oxycblt/musikr/Library.kt

@@ -27,6 +27,8 @@ interface Library {
     val genres: Collection<Genre>
     val playlists: Collection<Playlist>
 
+    fun empty(): Boolean
+
     fun findSong(uid: Music.UID): Song?
 
     fun findSongByPath(path: Path): Song?

musikr/src/main/java/org/oxycblt/musikr/model/LibraryImpl.kt

@@ -42,6 +42,8 @@ internal data class LibraryImpl(
     private val genreUidMap = genres.associateBy { it.uid }
     private val playlistUidMap = playlists.associateBy { it.uid }
 
+    override fun empty() = songs.isEmpty()
+
     override fun findSong(uid: Music.UID) = songUidMap[uid]
 
     override fun findSongByPath(path: Path) = songs.find { it.path == path }