Show empty library message properly

Fixes #8632
The `library` map still contains the default category even when "empty".

app/src/main/java/eu/kanade/tachiyomi/ui/library/LibraryScreen.kt

@@ -134,7 +134,7 @@ object LibraryScreen : Screen {
                 return@Scaffold
             }
 
-            if (state.searchQuery.isNullOrEmpty() && state.library.isEmpty()) {
+            if (state.searchQuery.isNullOrEmpty() && state.libraryCount == 0) {
                 val handler = LocalUriHandler.current
                 EmptyScreen(
                     textResource = R.string.information_empty_library,
@@ -156,7 +156,7 @@ object LibraryScreen : Screen {
                 selection = state.selection,
                 contentPadding = contentPadding,
                 currentPage = { screenModel.activeCategory },
-                isLibraryEmpty = state.library.isEmpty(),
+                isLibraryEmpty = state.libraryCount == 0,
                 showPageTabs = state.showCategoryTabs,
                 onChangeCurrentPage = { screenModel.activeCategory = it },
                 onMangaClicked = { router.openManga(it) },

app/src/main/java/eu/kanade/tachiyomi/ui/library/LibraryScreenModel.kt

@@ -10,6 +10,7 @@ import cafe.adriel.voyager.core.model.coroutineScope
 import eu.kanade.core.prefs.CheckboxState
 import eu.kanade.core.prefs.PreferenceMutableState
 import eu.kanade.core.prefs.asState
+import eu.kanade.core.util.fastDistinctBy
 import eu.kanade.core.util.fastFilter
 import eu.kanade.core.util.fastFilterNot
 import eu.kanade.core.util.fastMapNotNull
@@ -750,7 +751,7 @@ class LibraryScreenModel(
         val libraryCount by lazy {
             library
                 .flatMap { (_, v) -> v }
-                .distinctBy { it.libraryManga.manga.id }
+                .fastDistinctBy { it.libraryManga.manga.id }
                 .size
         }