Quitting pry-shell during active session crashes main application

[jacob-carlborg-apoex]

Steps to reproduce:

1. Start pry-shell
2. Set a breakpoint in an application
3. Trigger the breakpoint
4. In the pry-shell, run the \m command to get back to the main menu
5. Quit pry-shell
6. The main application crashes with the following error:

gems/drb-2.2.1/lib/drb/drb.rb:744:in `rescue in block in open': druby://localhost:1881 - #<Errno::ECONNREFUSED: Connection refused - connect(2) for "localhost" port 1881> (DRb::DRbConnError)
	from gems/drb-2.2.1/lib/drb/drb.rb:738:in `block in open'
	from gems/drb-2.2.1/lib/drb/drb.rb:737:in `each'
	from gems/drb-2.2.1/lib/drb/drb.rb:737:in `open'
	from gems/drb-2.2.1/lib/drb/drb.rb:1319:in `initialize'
	from gems/drb-2.2.1/lib/drb/drb.rb:1302:in `new'
	from gems/drb-2.2.1/lib/drb/drb.rb:1302:in `open'
	from gems/drb-2.2.1/lib/drb/drb.rb:1143:in `block in method_missing'
	from gems/drb-2.2.1/lib/drb/drb.rb:1162:in `with_friend'
	from gems/drb-2.2.1/lib/drb/drb.rb:1142:in `method_missing'
	from gems/pry-shell-0.6.4/lib/pry/shell/session.rb:53:in `block in pry_options'
	from gems/pry-shell-0.6.4/lib/pry/shell.rb:51:in `remove_active_connection!'
	from gems/pry-shell-0.6.4/lib/pry/shell/patches/pry_byebug.rb:19:in `teardown!'
	from gems/pry-shell-0.6.4/lib/pry/shell/patches/pry_byebug.rb:15:in `block in start'