Fix wrongly used CFile::Exists() for directories instead of CDirectory::Exists()
Currently it can cause hardly detectable errors as some VFS don't return true when directory is requested for CFile. One of VFS of such kind is Win32File.
Merge pull request #5349 from Karlson2k/vfs_fix_exists_01

Fix wrongly used CFile::Exists() for directories instead of CDirectory::Exists()