utils/tar: fix validation for tar without directory or extensions
utils/tar: fix validation for tar without directory or extensions

nandub/brew,JCount/brew,MikeMcQuaid/brew,claui/brew,JCount/brew,Homebrew/brew,EricFromCanada/brew,Homebrew/brew,claui/brew,EricFromCanada/brew,claui/brew,Homebrew/brew,MikeMcQuaid/brew,JCount/brew,MikeMcQuaid/brew,nandub/brew,EricFromCanada/brew,nandub/brew,EricFromCanada/brew,claui/brew,Homebrew/brew,MikeMcQuaid/brew,nandub/brew,JCount/brew