cabana: fixed segfault when search in signals (#28078)

tools/cabana/signalview.cc

@@ -599,21 +599,23 @@ void SignalView::updateState(const QHash<MessageId, CanData> *msgs) {
     max_value_width = std::max(max_value_width, fontMetrics().width(item->sig_val));
   }
 
+  QModelIndex top = tree->indexAt(QPoint(0, 0));
+  if (top.isValid()) {
     // update visible sparkline
+    int first_visible_row = top.parent().isValid() ? top.parent().row() + 1 : top.row();
+    int last_visible_row = model->rowCount() - 1;
+    QModelIndex bottom = tree->indexAt(tree->viewport()->rect().bottomLeft());
+    if (bottom.isValid()) {
+      last_visible_row = bottom.parent().isValid() ? bottom.parent().row() : bottom.row();
+    }
+
     QSize size(tree->columnWidth(1) - delegate->button_size.width(), delegate->button_size.height());
     int min_max_width = std::min(size.width() - 10, QFontMetrics(delegate->minmax_font).width("-000.00") + 5);
     int value_width = std::min<int>(max_value_width, size.width() * 0.35);
     size -= {value_width + min_max_width, style()->pixelMetric(QStyle::PM_FocusFrameVMargin) * 2};
 
-  QModelIndex top = tree->indexAt(QPoint(0, 0));
-  QModelIndex bottom = tree->indexAt(tree->viewport()->rect().bottomLeft());
-  int start_row = top.parent().isValid() ? top.parent().row() + 1 : top.row();
-  int end_row = model->rowCount() - 1;
-  if (bottom.isValid()) {
-    end_row = bottom.parent().isValid() ? bottom.parent().row() : bottom.row();
-  }
     QFutureSynchronizer<void> synchronizer;
-  for (int i = start_row; i <= end_row; ++i) {
+    for (int i = first_visible_row; i <= last_visible_row; ++i) {
       auto item = model->getItem(model->index(i, 1));
       auto &s = item->sparkline;
       if (s.last_ts != last_msg.ts || s.size() != size || s.time_range != settings.sparkline_range) {
@@ -621,7 +623,7 @@ void SignalView::updateState(const QHash<MessageId, CanData> *msgs) {
             &s, &Sparkline::update, model->msg_id, item->sig, last_msg.ts, settings.sparkline_range, size));
       }
     }
-  synchronizer.waitForFinished();
+  }
 
   for (int i = 0; i < model->rowCount(); ++i) {
     emit model->dataChanged(model->index(i, 1), model->index(i, 1), {Qt::DisplayRole});