Use less nullptr for empty flags

Change-Id: Ic4eafdc8f204a432a752a97593380609a408a7de
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/debugger/sourcefileshandler.cpp

@@ -78,7 +78,7 @@ QVariant SourceFilesHandler::headerData(int section,
 Qt::ItemFlags SourceFilesHandler::flags(const QModelIndex &index) const
 {
     if (index.row() >= m_fullNames.size())
-        return nullptr;
+        return {};
     QFileInfo fi(m_fullNames.at(index.row()));
     return fi.isReadable() ? QAbstractItemModel::flags(index) : Qt::ItemFlags({});
 }