Rename and clear bad code

src/randomizer.rs

@@ -20,7 +20,7 @@ pub enum RandomizerMessage {
 }
 
 impl NavigatedPage<RandomizerMessage> for RandomizerState {
-    fn navigate(&self, message: &RandomizerMessage) -> Option<Page> {
+    fn navigate(&mut self, message: &RandomizerMessage) -> Option<Page> {
         if let Back = message {
             return Some(Page::PreviousPage);
         }