Blur: Default disabled in pre-O devices

Signed-off-by: Fung Gwo <fython@163.com>

Author: fython

mobile/src/main/kotlin/info/papdt/express/helper/support/PTSettings.kt

@@ -29,7 +29,10 @@ class PTSettings(context: Context): SharedPreferencesProvider(context, "settings
 
 	var usingNewDatabase by booleanValue(defValue = false)
 
-	var enableAddDialogBackgroundBlur by booleanValue(defValue = true)
+	var enableAddDialogBackgroundBlur by booleanValue(
+            // Default disabled in pre-O devices
+			defValue = Build.VERSION.SDK_INT >= Build.VERSION_CODES.O
+	)
 
     var lastFilter by intValue(defValue = HomePackageListAdapter.FILTER_ON_THE_WAY)