fix: use default style so the workspaces view is not transparent

src/main.rs

@@ -587,6 +587,12 @@ impl Application for App {
     fn core_mut(&mut self) -> &mut cosmic::app::Core {
         &mut self.core
     }
+
+    fn style(
+        &self,
+    ) -> Option<<cosmic::Theme as cosmic::iced_style::application::StyleSheet>::Style> {
+        Some(cosmic::theme::style::iced::Application::default())
+    }
 }
 
 pub fn main() -> iced::Result {