Fixing some code problems

src/writing.rs

@@ -30,7 +30,7 @@ impl NavigatedPage<WritingMessage> for WritingState {
     fn navigated(&mut self) {}
     fn update(&mut self, message: WritingMessage) -> Task<RootMessage> {
         match message {
-            WritingMessage::Back => todo!(),
+            WritingMessage::Back => {},
             WritingMessage::Next => self.next(),
             WritingMessage::SwitchShowMode(b) => self.show_all = b,
         }