[syslinux] Avoid returning to menu if boot error happened

[Ady]

> After I removed the UI I am able to see the boot error message.
 
If the error is related to Syslinux, could you please post it here? 
Is it still happening?

BTW, since the Syslinux package in ArchLinux is currently built with 
less debugging options than the official upstream binaries, perhaps 
you might want to consider testing the latter, so to see whether the 
behavior and the (error) messages are the same.

Regards,
Ady.