Is there a reason you want to stop the package if there is no file? If there is no file, package wouldn't do anything anyways and just complete. No need to do anything.

If there is a reason to stop the package, Check out the link below. Use a script task to check for a file then write to a boolean variable. Then use the variable in precedence constraint redirect package to stop. Let me know if this makes sense.

https://msdn.microsoft.com/en-us/library/system.io.file.exists(v=vs.110).aspx