todomvc example: Disallow entering empty items (#3193)

It was possible to add an empty entry by typing whitespace into the
text field. This fixes that by trimming the string *before* we check
whether it's empty.

examples/todomvc/src/main.rs

@@ -45,9 +45,10 @@ impl Component for App {
     fn update(&mut self, _ctx: &Context<Self>, msg: Self::Message) -> bool {
         match msg {
             Msg::Add(description) => {
+                let description = description.trim();
                 if !description.is_empty() {
                     let entry = Entry {
-                        description: description.trim().to_string(),
+                        description: description.to_string(),
                         completed: false,
                         editing: false,
                     };