[Remanga] Fix parsing manga without covers

src/main/kotlin/org/koitharu/kotatsu/parsers/site/ru/RemangaParser.kt

@@ -112,8 +112,8 @@ internal class RemangaParser(
 				title = jo.getString("rus_name"),
 				altTitles = setOfNotNull(jo.getStringOrNull("en_name")),
 				rating = jo.getString("avg_rating").toFloatOrNull()?.div(10f) ?: RATING_UNKNOWN,
-				coverUrl = "https://api.$domain${img.getString("mid")}",
+				coverUrl = img.getStringOrNull("mid")?.toAbsoluteUrl("api.$domain"),
-				largeCoverUrl = "https://api.$domain${img.getString("high")}",
+				largeCoverUrl = img.getStringOrNull("high")?.toAbsoluteUrl("api.$domain"),
 				authors = emptySet(),
 				contentRating = null,
 				state = null,