fix(radarr): show a loading block while the updates popup refreshes

The updates popup only checked whether its text was empty, so during a
refresh it kept rendering the previously fetched text. Opening the system
updates view dispatches a request for the update notes, so the popup could
sit on stale content until the response landed.

Guard on the loading flag as well, matching the sonarr, lidarr and readarr
updates popups, and add the loading-state test those trees have so both
halves of the condition are exercised. The pre-existing empty-updates test
never reaches the second half on its own.

src/ui/radarr_ui/system/snapshots/managarr__ui__radarr_ui__system__system_details_ui__system_details_ui_tests__tests__snapshot_tests__system_details_ui_updates_popup_is_loading_when_updates_are_present.snap

@@ -0,0 +1,48 @@
+---
+source: src/ui/radarr_ui/system/system_details_ui_tests.rs
+expression: output
+---
+                                                                                                                                                                     
+                                                                                                                                                                     
+                                                                                                                                                                     
+                                                                                                                                                                     
+                                                                                                                                                                     
+                                                                                                                                                                     
+                    ╭  Updates  ───────────────────────────────────────────────────────────────────────────────────────────────────────────────╮                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │ Loading ...                                                                                                              │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    │                                                                                                                          │                     
+                    ╰──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯

src/ui/radarr_ui/system/system_details_ui.rs

@@ -126,7 +126,7 @@ fn draw_updates_popup(f: &mut Frame<'_>, app: &mut App<'_>) {
   let updates = app.data.radarr_data.updates.get_text();
   let block = title_block("Updates");
 
-  if !updates.is_empty() {
+  if !updates.is_empty() && !app.is_loading {
     let updates_paragraph = Paragraph::new(Text::from(updates))
       .block(borderless_block())
       .scroll((app.data.radarr_data.updates.offset, 0));

src/ui/radarr_ui/system/system_details_ui_tests.rs

@@ -87,6 +87,21 @@ mod tests {
       insta::assert_snapshot!(output);
     }
 
+    #[test]
+    fn test_system_details_ui_updates_popup_is_loading_when_updates_are_present() {
+      let mut app = App::test_default_fully_populated();
+      app.is_loading = true;
+      app.push_navigation_stack(ActiveRadarrBlock::SystemUpdates.into());
+
+      assert!(!app.data.radarr_data.updates.get_text().is_empty());
+
+      let output = render_to_string_with_app(TerminalSize::Large, &mut app, |f, app| {
+        SystemDetailsUi::draw(f, app, f.area());
+      });
+
+      insta::assert_snapshot!(output);
+    }
+
     #[test]
     fn test_system_details_ui_renders_updates_loading_when_empty() {
       let mut app = App::test_default_fully_populated();