When removing the subpaths of an external path, we first need to check
if a subpath is not versioned instead of checking if it is empty.
If a subpath is versioned, we can stop the paths removal process.
Relate to T3870
Fixes SWH-LOADER-SVN-53, SWH-LOADER-SVN-55 and SWH-LOADER-SVN-57.
Depends on D7015