[Madara] Fix multiple pages handling

src/main/kotlin/org/koitharu/kotatsu/parsers/site/madara/MadaraParser.kt

@@ -678,8 +678,8 @@ internal abstract class MadaraParser(
 					"No image found, try to log in",
 					fullUrl,
 				)
-				return root.select(selectPage).map { div ->
+				return root.select(selectPage).flatMap { div ->
-					val img = div.selectFirstOrThrow("img")
+					div.selectOrThrow("img").map { img ->
 						val url = img.src()?.toRelativeUrl(domain) ?: div.parseFailed("Image src not found")
 						MangaPage(
 							id = generateUid(url),
@@ -689,6 +689,7 @@ internal abstract class MadaraParser(
 						)
 					}
 				}
+			}
 		} else {
 
 			val chapterProtectorHtml = chapterProtector.attr("src")