cask/cmd/info: Fix crash when using --github with a formula
cask/cmd/info: Fix crash when using --github with a formula

Homebrew/brew,reitermarkus/brew,vitorgalvao/brew,vitorgalvao/brew,vitorgalvao/brew,nandub/brew,nandub/brew,reitermarkus/brew,claui/brew,sjackman/homebrew,EricFromCanada/brew,EricFromCanada/brew,JCount/brew,Homebrew/brew,sjackman/homebrew,konqui/brew,claui/brew,claui/brew,Homebrew/brew,claui/brew,Homebrew/brew,JCount/brew,reitermarkus/brew,reitermarkus/brew,MikeMcQuaid/brew,konqui/brew,EricFromCanada/brew,konqui/brew,MikeMcQuaid/brew,JCount/brew,JCount/brew,MikeMcQuaid/brew,sjackman/homebrew,MikeMcQuaid/brew,vitorgalvao/brew,EricFromCanada/brew,nandub/brew,konqui/brew,sjackman/homebrew,nandub/brew