fix: 朗读引擎储存

app/src/main/java/io/legado/app/help/config/AppConfig.kt

@@ -478,9 +478,9 @@ object AppConfig : SharedPreferences.OnSharedPreferenceChangeListener {
         }
 
     var ttsEngine: String?
-        get() = appCtx.getPrefString(PreferKey.ttsEngine)
+        get() = io.legado.app.ui.config.readConfig.ReadConfig.ttsEngine
         set(value) {
-            appCtx.putPrefString(PreferKey.ttsEngine, value)
+            io.legado.app.ui.config.readConfig.ReadConfig.ttsEngine = value
         }
 
     var webPort: Int

app/src/main/java/io/legado/app/ui/config/readConfig/ReadConfig.kt

@@ -241,4 +241,9 @@ object ReadConfig {
         PreferKey.ttsSpeechRate,
         5
     )
+
+    var ttsEngine by prefDelegate<String?>(
+        PreferKey.ttsEngine,
+        null
+    )
 }