QFileSystemModel sorts . and .. not perfectly

By default QFileSystemModel does not show . and .. items, but it does with setFilter(QDir::AllEntries | QDir::AllDirs). QFileSystemModel sorts items using QFileSystemModelSorter. QFileSystemModelSorter does not treat . and .. as special items and sort them along with other directories lexicographically, which means that if directory contains subdirectories with names that starts for example with parenthesis this subdirectories will be displayed above . and ..
In attachement program that demonstrates this issue, screenshot and suggested patch.