修复未在书架时，退出阅读界面时弹窗两次的问题

app/src/main/java/io/legato/kazusa/ui/book/read/ReadBookActivity.kt

@@ -311,7 +311,7 @@ class ReadBookActivity : BaseReadBookActivity(),
             if (getPrefBoolean("disableReturnKey") && !menuLayoutIsVisible) {
                 return@addCallback
             }
-            if (savedInstanceState != null) {
+            if (savedInstanceState != null || !ReadBook.inBookshelf) {
                 finish()
             } else {
                 supportFinishAfterTransition()