Use MangaImpl defaults in Manga.create() (#7538)

app/src/main/java/eu/kanade/domain/manga/model/Manga.kt

@@ -133,11 +133,11 @@ data class Manga(
             title = "",
             source = -1L,
             favorite = false,
-            lastUpdate = -1L,
-            dateAdded = -1L,
-            viewerFlags = -1L,
+            lastUpdate = 0L,
+            dateAdded = 0L,
+            viewerFlags = 0L,
             chapterFlags = 0L,
-            coverLastModified = -1L,
+            coverLastModified = 0L,
             artist = null,
             author = null,
             description = null,