cabana: fix stuck on exit (#29796)

fix ctrl+c can't exit when stream dialog displayed on startup

tools/cabana/cabana.cc

@@ -75,12 +75,7 @@ int main(int argc, char *argv[]) {
     } else if (cmd_parser.isSet("demo")) {
       route = DEMO_ROUTE;
     }
-
-    if (route.isEmpty()) {
-      StreamSelector dlg(&stream);
-      dlg.exec();
-      dbc_file = dlg.dbcFile();
-    } else {
+    if (!route.isEmpty()) {
       auto replay_stream = new ReplayStream(&app);
       if (!replay_stream->loadRoute(route, cmd_parser.value("data_dir"), replay_flags)) {
         return 0;
@@ -89,7 +84,15 @@ int main(int argc, char *argv[]) {
     }
   }
 
+  int ret = 0;
+  {
     MainWindow w;
+    QTimer::singleShot(0, [&]() {
+      if (!stream) {
+        StreamSelector dlg(&stream);
+        dlg.exec();
+        dbc_file = dlg.dbcFile();
+      }
       if (!stream) {
         stream = new DummyStream(&app);
       }
@@ -98,8 +101,11 @@ int main(int argc, char *argv[]) {
         w.loadFile(dbc_file);
       }
       w.show();
+    });
+
+    ret = app.exec();
+  }
 
-  int ret = app.exec();
   delete can;
   return ret;
 }