Had that too rancho, a clean install of archlinux fixed it for me :|
Here's how to check if a file exists for a client
The "FileExists" function is server only, as stupid as that is.
For the "ForEachFile" sintax, just type the command in console.
The "file_exists" variable is a custom one, but there are other "file_*" variables that are used by the "ForEachFile" command if you are interested in having a look.
Set file_exists false
ForEachFile * /path/to/file filename true "Set file_exists true"
You can also GetCheckSum but it prints an error if file is not found.