Nested config applies defaults even when specified

• nested configs initialize with defaults and then are reconfigured, evidently. this means incorrect defaults cannot be used: Given this task:

  require 'tap/task'

  # Request::task
  class Request < Tap::Task
    nest :a do
      config :b, nil, &c.integer
    end
  
    def process
      puts a.b
    end
  end

This will result

% rap request --a:b 1
expected [Integer] but was: nil

Normally if a switch is specified on the command line, the default will not be applied. This allows the rare case where you want an invalid default. Evidently nested configs initialize with defaults and then are reconfigured, and this should not be the case.