Rename and clear bad code

src/history.rs

@@ -18,7 +18,7 @@ pub struct HistoryState {
 }
 
 impl NavigatedPage<HistoryMessage> for HistoryState {
-    fn navigate(&self, message: &HistoryMessage) -> Option<Page> {
+    fn navigate(&mut self, message: &HistoryMessage) -> Option<Page> {
         match message {
             Back => Some(Page::PreviousPage),
         }