Don't persist blueprints for unknown apps (#2165)

* Don't persist the blueprint for unknown app ids

* Less prominent text when no time has been selected

crates/re_viewer/src/app.rs

@@ -115,14 +115,20 @@ impl App {
             );
         }
 
-        let state: AppState = if startup_options.persist_state {
+        let mut state: AppState = if startup_options.persist_state {
             storage
                 .and_then(|storage| eframe::get_value(storage, eframe::APP_KEY))
                 .unwrap_or_default()
         } else {
             AppState::default()
         };
 
+        // Forget the blueprint we used for some unknown app,
+        // so we don't reuse it for some unrelated unknown app.
+        // This is in particularly important for `rerun foo.png`
+        // followed by `rerun bar.png`, which both uses the unknow App ID.
+        state.blueprints.remove(&ApplicationId::unknown());
+
         let mut analytics = ViewerAnalytics::new();
         analytics.on_viewer_started(&build_info, app_env);
 

crates/re_viewer/src/ui/viewport.rs

@@ -770,7 +770,7 @@ fn space_view_ui(
 ) {
     let Some(latest_at) = ctx.rec_cfg.time_ctrl.time_int() else {
         ui.centered_and_justified(|ui| {
-            ui.label(ctx.re_ui.warning_text("No time selected"));
+            ui.weak("No time selected");
         });
         return
     };