I can't say I'm sure of when a script needs to be halted, or when it's going to halt itself, it seems safer to just add the line than to not. I can't see it hurting anything. Furthermore, when several if statements works just as well as ifelse and else, why use them and create something more confusing? The idea of my scripts most of the time isn't absolute speed, functionality, or properness. They're about me being able to understand them, how I wrote them, know exactly what they do, and they do what I want.
