Clear with ui.menu style before rendering menu

When rendering a completion popup, the popup component will clear
the area with ui.popup and then the menu component would draw over
it using a table component. We remove the left edge of the area
before passing it to the table component (so that it will be left
as padding), and the table component uses ui.menu as the style.
If ui.menu and ui.popup are different the left edge of the popup
will look different from the rest of the popup. We avoid this by
clearing the whole area with ui.menu in Menu::render

helix-term/src/ui/menu.rs

@@ -274,6 +274,7 @@ impl<T: Item + 'static> Component for Menu<T> {
             .try_get("ui.menu")
             .unwrap_or_else(|| theme.get("ui.text"));
         let selected = theme.get("ui.menu.selected");
+        surface.clear_with(area, style);
 
         let scroll = self.scroll;