Bug in else without a rescue

[JoshCheek]

Initially opened as #304. Adding a new issue b/c it seems to have a bug in its implementation:

# Latest Parser (as of 26 Sept)
$ ruby-parse -v
ruby-parse based on parser version 2.3.1.4

This bit works fine:

# Ruby has no issue
$ ruby -e 'begin; rescue; else; p 1; end'
1


# Parser makes it a second child of `rescue`
$ ruby-parse -e 'def a; rescue; else; p 1; end; a'
warning: parser/current is loading parser/ruby22, which recognizes
warning: 2.2.5-compliant syntax, but you are running 2.2.2.
warning: please see https://github.com/whitequark/parser#compatibility-with-ruby-mri.
(kwbegin
  (rescue nil
    (resbody nil nil nil)
    (send nil :p
      (int 1))))

This one has a bug, compound_stmt is nil (I'd look into it, but there's a television on and two dogs running around, so it's difficult to concentrate)

# Ruby dislikes it, but still runs it
$ ruby -e 'begin; else; p 1; end'
-e:1: warning: else without rescue is useless
1


# Parser explodes with a NoMethodError
$ ruby-parse -e 'begin; else; p 1; end'
warning: parser/current is loading parser/ruby22, which recognizes
warning: 2.2.5-compliant syntax, but you are running 2.2.2.
warning: please see https://github.com/whitequark/parser#compatibility-with-ruby-mri.
Failed on: (fragment:0)
/Users/josh/.gem/ruby/2.2.2/gems/parser-2.3.1.4/lib/parser/builders/default.rb:987:in `begin_body': undefined method `type' for nil:NilClass (NoMethodError)
    from /Users/josh/.gem/ruby/2.2.2/gems/parser-2.3.1.4/lib/parser/ruby22.rb:3387:in `_reduce_9'
    from /Users/josh/.rubies/ruby-2.2.2/lib/ruby/2.2.0/racc/parser.rb:258:in `_racc_do_parse_c'
    from /Users/josh/.rubies/ruby-2.2.2/lib/ruby/2.2.0/racc/parser.rb:258:in `do_parse'
    from /Users/josh/.gem/ruby/2.2.2/gems/parser-2.3.1.4/lib/parser/base.rb:162:in `parse'
    from /Users/josh/.gem/ruby/2.2.2/gems/parser-2.3.1.4/lib/parser/runner/ruby_parse.rb:132:in `process'
    from /Users/josh/.gem/ruby/2.2.2/gems/parser-2.3.1.4/lib/parser/runner.rb:207:in `process_buffer'
    from /Users/josh/.gem/ruby/2.2.2/gems/parser-2.3.1.4/lib/parser/runner.rb:181:in `block in process_fragments'
    from /Users/josh/.gem/ruby/2.2.2/gems/parser-2.3.1.4/lib/parser/runner.rb:173:in `each'
    from /Users/josh/.gem/ruby/2.2.2/gems/parser-2.3.1.4/lib/parser/runner.rb:173:in `each_with_index'
    from /Users/josh/.gem/ruby/2.2.2/gems/parser-2.3.1.4/lib/parser/runner.rb:173:in `process_fragments'
    from /Users/josh/.gem/ruby/2.2.2/gems/parser-2.3.1.4/lib/parser/runner.rb:163:in `block in process_all_input'
    from /Users/josh/.rubies/ruby-2.2.2/lib/ruby/2.2.0/benchmark.rb:288:in `measure'
    from /Users/josh/.gem/ruby/2.2.2/gems/parser-2.3.1.4/lib/parser/runner.rb:162:in `process_all_input'
    from /Users/josh/.gem/ruby/2.2.2/gems/parser-2.3.1.4/lib/parser/runner/ruby_parse.rb:128:in `process_all_input'
    from /Users/josh/.gem/ruby/2.2.2/gems/parser-2.3.1.4/lib/parser/runner.rb:33:in `execute'
    from /Users/josh/.gem/ruby/2.2.2/gems/parser-2.3.1.4/lib/parser/runner.rb:11:in `go'
    from /Users/josh/.gem/ruby/2.2.2/gems/parser-2.3.1.4/bin/ruby-parse:6:in `<top (required)>'
    from /Users/josh/.gem/ruby/2.2.2/bin/ruby-parse:23:in `load'
    from /Users/josh/.gem/ruby/2.2.2/bin/ruby-parse:23:in `<main>'