Fix reader bug with new suspend getFlatMetadata

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

@@ -247,15 +247,12 @@ class ReaderPresenter(
             .first()
             .observeOn(AndroidSchedulers.mainThread())
             // SY -->
-            .flatMap { manga ->
+            .map { manga ->
                 val source = sourceManager.get(manga.source)?.getMainSource()
                 if (manga.initialized && source is MetadataSource<*, *>) {
-                    db.getFlatMetadataForManga(mangaId).asRxSingle().map {
-                        manga to it?.raise(source.metaClass)
-                    }.toObservable()
-                } else {
-                    Observable.just(manga to null)
-                }
+                    val flatMeta = db.getFlatMetadataForManga(mangaId).executeAsBlocking()
+                    manga to flatMeta?.raise(source.metaClass)
+                } else manga to null
             }
             .doOnNext { init(it.first, initialChapterId, it.second) }
             // SY <--