Fix Issue #8298, Don't throw exceptions on broken symlinks.

Using dirEntries to loop trough all the files/directories in a directory
will curently throw an Exception when encountering an broken symlink.

Whit this change DirEntry will no longer throw an Exception for broken
symlinks, but in that case isDir and isFile will return flase while
isSymlink returns true.
Merge pull request #1142 from MikeWey/Issue8298

Fix Issue #8298, Don't throw exceptions on broken symlinks.