remember saved default value for screen mode

frontend/apps/reader/modules/readerview.lua

@@ -575,8 +575,13 @@ function ReaderView:onToggleScrollMode(page_scroll)
 end
 
 function ReaderView:onReadSettings(config)
+    local screen_mode
     self.render_mode = config:readSetting("render_mode") or 0
-    local screen_mode = config:readSetting("screen_mode") or "portrait"
+    if self.ui.document.info.has_pages then
+        screen_mode = config:readSetting("screen_mode") or G_reader_settings:readSetting("kopt_screen_mode") or "portrait"
+    else
+        screen_mode = config:readSetting("screen_mode") or G_reader_settings:readSetting("copt_screen_mode") or "portrait"
+    end
     if screen_mode then
         Screen:setScreenMode(screen_mode)
         self:onSetScreenMode(screen_mode, config:readSetting("rotation_mode"))