Minor cleanup

app/src/main/java/eu/kanade/tachiyomi/ui/browse/extension/details/ExtensionDetailsScreenModel.kt

@@ -173,7 +173,7 @@ data class ExtensionDetailsState(
 ) {
 
     val sources: List<ExtensionSourceItem>
-        get() = _sources ?: emptyList()
+        get() = _sources.orEmpty()
 
     val isLoading: Boolean
         get() = extension == null || _sources == null

app/src/main/java/eu/kanade/tachiyomi/ui/browse/migration/manga/MigrationMangaScreenModel.kt

@@ -64,7 +64,7 @@ data class MigrateMangaState(
 ) {
 
     val titles: List<Manga>
-        get() = titleList ?: emptyList()
+        get() = titleList.orEmpty()
 
     val isLoading: Boolean
         get() = source == null || titleList == null

app/src/main/java/eu/kanade/tachiyomi/ui/browse/source/browse/BrowseSourceScreenModel.kt

@@ -311,7 +311,7 @@ class BrowseSourceScreenModel(
         return getCategories.subscribe()
             .firstOrNull()
             ?.filterNot { it.isSystemCategory }
-            ?: emptyList()
+            .orEmpty()
     }
 
     suspend fun getDuplicateLibraryManga(manga: Manga): Manga? {

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

@@ -355,7 +355,7 @@ class LibraryScreenModel(
                 categories
             }
 
-            displayCategories.associateWith { libraryManga[it.id] ?: emptyList() }
+            displayCategories.associateWith { libraryManga[it.id].orEmpty() }
         }
     }
 
@@ -700,7 +700,7 @@ class LibraryScreenModel(
         }
 
         fun getLibraryItemsByPage(page: Int): List<LibraryItem> {
-            return library.values.toTypedArray().getOrNull(page) ?: emptyList()
+            return library.values.toTypedArray().getOrNull(page).orEmpty()
         }
 
         fun getMangaCountForCategory(category: Category): Int? {

app/src/main/java/eu/kanade/tachiyomi/ui/reader/loader/DirectoryPageLoader.kt

@@ -25,7 +25,8 @@ class DirectoryPageLoader(val file: File) : PageLoader() {
                     stream = streamFn
                     status = Page.State.READY
                 }
-            } ?: emptyList()
+            }
+            .orEmpty()
     }
 
     /**