Submitting forms with empty selects yields 'null' string literal

[jadefish]

If a form contains a <select> with no <option> elements, submitting the form yields a corresponding key-value pair with a string literal 'null' value. Non-empty selects and empty non-select elements yield the empty string.

Example:

form do
  select name: :select1 do
    label 'Select1'

    # first item selected by default:
    some_array.each_with_index do |item, i|
      option text: item, value: i
    end
  end

  select name: :select2 do
    label 'Select2'

    # no options:
    [].each_with_index do |item, i|
      option text: item, value: i
    end
  end

  button 'Submit' do
    creates some_path, redirect: some_other_path
  end
end

Submitting the above form yields:

select1: 0
select2: "null"