这个null不要改,方便导出后确认哪些章节没有下载

app/src/main/java/io/legado/app/ui/book/cache/CacheViewModel.kt

@@ -163,7 +163,7 @@ class CacheViewModel(application: Application) : BaseViewModel(application) {
                     .getContent(
                         book,
                         chapter,
-                        content ?: "",
+                        content ?: "null",
                         includeTitle = !AppConfig.exportNoChapterName,
                         useReplace = useReplace,
                         chineseConvert = false,
@@ -419,7 +419,7 @@ class CacheViewModel(application: Application) : BaseViewModel(application) {
             upAdapterLiveData.postValue(book.bookUrl)
             exportProgress[book.bookUrl] = index
             BookHelp.getContent(book, chapter).let { content ->
-                var content1 = fixPic(epubBook, book, content ?: "", chapter)
+                var content1 = fixPic(epubBook, book, content ?: "null", chapter)
                 content1 = contentProcessor
                     .getContent(
                         book,