修复自动换源的bug

app/src/main/java/io/legado/app/service/help/ReadBook.kt

@@ -264,8 +264,9 @@ object ReadBook {
 
     private fun download(chapter: BookChapter, resetPageOffset: Boolean) {
         book?.let { book ->
-            webBook?.getContent(book, chapter)
-                ?.onSuccess(Dispatchers.IO) { content ->
+            webBook?.let {
+                it.getContent(book, chapter)
+                    .onSuccess(Dispatchers.IO) { content ->
                         if (content.isEmpty()) {
                             contentLoadFinish(
                                 book,
@@ -276,10 +277,15 @@ object ReadBook {
                             removeLoading(chapter.index)
                         } else {
                             BookHelp.saveContent(book, chapter, content)
-                        contentLoadFinish(book, chapter, content, resetPageOffset = resetPageOffset)
+                            contentLoadFinish(
+                                book,
+                                chapter,
+                                content,
+                                resetPageOffset = resetPageOffset
+                            )
                             removeLoading(chapter.index)
                         }
-                }?.onError {
+                    }.onError {
                         contentLoadFinish(
                             book,
                             chapter,
@@ -288,7 +294,16 @@ object ReadBook {
                         )
                         removeLoading(chapter.index)
                     }
+            } ?: let {
+                contentLoadFinish(
+                    book,
+                    chapter,
+                    "没有书源",
+                    resetPageOffset = resetPageOffset
+                )
+                removeLoading(chapter.index)
             }
+        } ?: removeLoading(chapter.index)
     }
 
     private fun addLoading(index: Int): Boolean {