given arg_one require arg_two of array -> auto passes empty string to array when empty array is given

desc 'Breaking Grape', security: [jwt: []], success: { code: 201, model: SomeRepresenter }
      params do
        with documentation: { param_type: 'body' } do
          requires :arg_one, type: String, values: %w[one two three]
          given arg_one: ->(type) { type == 'two' } do
            requires :arg_two, type: Array[String], allow_blank: false
          end
        end
      end
end

POST to that endpoint with { "arg_one": "two", "arg_two": [] }
and somehow the array will contain an empty string. Fails both with allow_blank false and allow_blank.

How does the empty string end up there?
How does it not fail when allow_blank false?

Start by reproducing the POST request against the params block using arg_one set to "two" and arg_two set to an empty array. Trace the handling of the conditional requires declaration and verify that an empty array does not gain an empty-string element and that allow_blank: false produces the intended validation result.