fix about-page history issue

src/components/DictionaryView.vue

@@ -355,8 +355,8 @@ export default {
         self.article = event.state.article
         self.search_results = event.state.search_results
         self.lang = event.state.lang
-        self.pos_selected = event.pos_selected
-        self.scope = event.scope
+        self.pos_selected = event.pos_selected || self.pos_selected
+        self.scope = event.scope || self.scope
         self.error = event.state.error
       }
     }