Not worked with grammars with parameters

[Mingun]

If ksy contains key params at top-level, then visualizer crashed with error:

$ ksv msg kaitai-struct/ddc.ksy 
Compilation OK
... processing kaitai-struct/ddc.ksy 0
...... loading ddc.rb
Classes loaded OK, main class = Ddc
/tmp/d20200109-15900-1lqithx/ddc.rb:12:in `initialize': wrong number of arguments (given 1, expected 2..4) (ArgumentError)
	from /var/lib/gems/2.3.0/gems/kaitai-struct-0.8/lib/kaitai/struct/struct.rb:26:in `new'
	from /var/lib/gems/2.3.0/gems/kaitai-struct-0.8/lib/kaitai/struct/struct.rb:26:in `from_file'
	from /var/lib/gems/2.3.0/gems/kaitai-struct-visualizer-0.7/lib/kaitai/struct/visualizer/parser.rb:28:in `load'
	from /var/lib/gems/2.3.0/gems/kaitai-struct-visualizer-0.7/lib/kaitai/struct/visualizer/visualizer.rb:13:in `run'
	from /var/lib/gems/2.3.0/gems/kaitai-struct-visualizer-0.7/bin/ksv:53:in `<top (required)>'
	from /usr/local/bin/ksv:23:in `load'
	from /usr/local/bin/ksv:23:in `<main>'

Generated struct has following definition:

class Ddc < Kaitai::Struct::Struct
  def initialize(_io, _parent = nil, _root = self, has_mac)
    super(_io, _parent, _root)
    @has_mac = has_mac
    _read
  end
  ...

Original ksv:

meta:
  id: ddc
params:
  - id: has_mac
    type: bool
seq:
  ...