Fix `nil` handling in `arch` cask DSL
Fix `nil` handling in `arch` cask DSL

Homebrew/brew,JCount/brew,JCount/brew,nandub/brew,Homebrew/brew,MikeMcQuaid/brew,nandub/brew,Homebrew/brew,nandub/brew,MikeMcQuaid/brew,JCount/brew,MikeMcQuaid/brew,JCount/brew,Homebrew/brew,MikeMcQuaid/brew,nandub/brew