Set alert_view action button visibility to false and update border-ra…

…dius in CSS

- Set `alert_view.action_button.visible` to `false` in `CategoryView.vala`.
- Update `border-radius` from `12px` to `24px` in `style.css`.

data/style.css

@@ -285,7 +285,7 @@ spinbutton.flat {
   font-weight: 900;
   color: #fff;
   background: alpha(@scrim, 0.32);
-  border-radius: 12px;
+  border-radius: 24px;
   font-feature-settings: 'tnum' 1;
 }
 

src/CategoryView.vala

@@ -32,6 +32,7 @@ namespace Fusebox {
 
         construct {
             alert_view = new He.EmptyPage ();
+            alert_view.action_button.visible = false;
 
             category = new Fusebox.Category ();