优化

app/src/main/java/io/legado/app/model/localBook/EpubFile.kt

@@ -311,6 +311,7 @@ class EpubFile(var book: Book) {
     ) {
         val contents = epubBook?.contents
         if (epubBook == null || contents == null || refs == null) return
+        val firstRef = refs.firstOrNull { it.resource != null } ?: return
         var i = 0
         durIndex = 0