fix bug with "-" flag
fix bug with "-" flag

the --debugger flag does not have a char attribute. This causes a bug
where if you run a command like `heroku info -a forker -` it will try to
run it with --debugger.

monkbroc/particle-cli-ng,monkbroc/particle-cli-ng,heroku/cli-engine,monkbroc/particle-cli-ng,monkbroc/particle-cli-ng,heroku/cli-engine,heroku/cli-engine