In some archives parent folders of some files might not be part of the archive themselves, i.e. the archive does not contain entries for them. In this case ArchiveModel creates ArchiveDirNodes for these folders. However, the FileName and InternalID properties of these folders do not get a trailing slash. This results in faulty root nodes leading to e.g. broken drag-n-drop extraction of files within these folders.

This diff simply appends a traling slash to the properties.

Solves bug:
https://bugs.kde.org/show_bug.cgi?id=367549

Meant for Applications/16.08 branch.

1. Open an archive which contains parentless files, e.g. the nested tar.gz archive within the attached archive in: https://bugs.kde.org/show_bug.cgi?id=367549
2. Drag-and-drop extract e.g. the file etc/nsswitch.conf