cabana: fix segfault when editing signal while filtering (#28836)

Fix the issue that editing signal will segfault when there is a filter string.
old-commit-hash: 1301e2d640

tools/cabana/signalview.cc

@@ -226,10 +226,14 @@ void SignalModel::handleMsgChanged(MessageId id) {
 
 void SignalModel::handleSignalAdded(MessageId id, const cabana::Signal *sig) {
   if (id == msg_id) {
+    if (filter_str.isEmpty()) {
       int i = dbc()->msg(msg_id)->indexOf(sig);
       beginInsertRows({}, i, i);
       insertItem(root.get(), i, sig);
       endInsertRows();
+    } else if (sig->name.contains(filter_str, Qt::CaseInsensitive)) {
+      refresh();
+    }
   }
 }
 
@@ -237,6 +241,7 @@ void SignalModel::handleSignalUpdated(const cabana::Signal *sig) {
   if (int row = signalRow(sig); row != -1) {
     emit dataChanged(index(row, 0), index(row, 1), {Qt::DisplayRole, Qt::EditRole, Qt::CheckStateRole});
 
+    if (filter_str.isEmpty()) {
       // move row when the order changes.
       int to = dbc()->msg(msg_id)->indexOf(sig);
       if (to != row) {
@@ -246,6 +251,7 @@ void SignalModel::handleSignalUpdated(const cabana::Signal *sig) {
       }
     }
   }
+}
 
 void SignalModel::handleSignalRemoved(const cabana::Signal *sig) {
   if (int row = signalRow(sig); row != -1) {