Puma dev command fails with type error due to nil

[cupakromer]

Issue

puma-dev command fails initial setup with TypeError:

Traceback (most recent call last):
    19: from bin/radius-cli:29:in `<main>'
    18: from bin/radius-cli:29:in `load'
    17: from .gem/ruby/2.5.3/bundler/gems/radius-cli-3176b3aff35c/exe/radius-cli:5:in `<top (required)>'
    16: from .gem/ruby/2.5.3/gems/thor-0.20.3/lib/thor/base.rb:466:in `start'
    15: from .gem/ruby/2.5.3/gems/thor-0.20.3/lib/thor.rb:387:in `dispatch'
    14: from .gem/ruby/2.5.3/gems/thor-0.20.3/lib/thor/invocation.rb:126:in `invoke_command'
    13: from .gem/ruby/2.5.3/gems/thor-0.20.3/lib/thor/command.rb:27:in `run'
    12: from .gem/ruby/2.5.3/gems/thor-0.20.3/lib/thor.rb:40:in `block in register'
    11: from .gem/ruby/2.5.3/gems/thor-0.20.3/lib/thor/invocation.rb:115:in `invoke'
    10: from .gem/ruby/2.5.3/gems/thor-0.20.3/lib/thor/group.rb:232:in `dispatch'
     9: from .gem/ruby/2.5.3/gems/thor-0.20.3/lib/thor/invocation.rb:133:in `invoke_all'
     8: from .gem/ruby/2.5.3/gems/thor-0.20.3/lib/thor/invocation.rb:133:in `map'
     7: from .gem/ruby/2.5.3/gems/thor-0.20.3/lib/thor/invocation.rb:133:in `each'
     6: from .gem/ruby/2.5.3/gems/thor-0.20.3/lib/thor/invocation.rb:133:in `block in invoke_all'
     5: from .gem/ruby/2.5.3/gems/thor-0.20.3/lib/thor/invocation.rb:126:in `invoke_command'
     4: from .gem/ruby/2.5.3/gems/thor-0.20.3/lib/thor/command.rb:27:in `run'
     3: from .gem/ruby/2.5.3/bundler/gems/radius-cli-3176b3aff35c/lib/radius/cli/puma_dev.rb:220:in `link_project'
     2: from .rubies/ruby-2.5.3/lib/ruby/2.5.0/pathname.rb:411:in `join'
     1: from .rubies/ruby-2.5.3/lib/ruby/2.5.0/pathname.rb:411:in `new'
.rubies/ruby-2.5.3/lib/ruby/2.5.0/pathname.rb:411:in `initialize': no implicit conversion of nil into String (TypeError)

Cause

The issue is caused by app_domain not being defined:

radius-cli/lib/radius/cli/puma_dev.rb

Lines 217 to 220 in 3176b3a

	def link_project
	puts "\nLinking project..."
	link_dir = Pathname("~/.puma-dev").expand_path
	link_path = link_dir.join(app_domain)