This patch fixes a few things...

If a modify task or modify variable dialog is not correctly filled in, now issues a poppup warning and drops the user back to the dialog - as opposed to issuing a poppup warning and closeing the dialog

Now checks for valid executable if absolute path is specifiedas well as if path is not specified and $PATH is used

Combines two seperate popups into one - one was for file not executable, one was for cron times not selected