Style/EmptyElse crash on master

[YayC]

source method:

def return_time
    if round_trip
      last_trip.scheduled_start_at
    else
      nil
    end
end

for rubocop:

undefined method `begin_pos' for #<Parser::Source::Map::Condition:0x007f971cdff970>
gems/rubocop-9cf9c3c91446/lib/rubocop/cached_data.rb:39:in `serialize_offense'
gems/rubocop-9cf9c3c91446/lib/rubocop/cached_data.rb:18:in `block in to_json'
gems/rubocop-9cf9c3c91446/lib/rubocop/cached_data.rb:18:in `map'
gems/rubocop-9cf9c3c91446/lib/rubocop/cached_data.rb:18:in `to_json'
gems/rubocop-9cf9c3c91446/lib/rubocop/result_cache.rb:93:in `block in save'
gems/rubocop-9cf9c3c91446/lib/rubocop/result_cache.rb:92:in `open'
gems/rubocop-9cf9c3c91446/lib/rubocop/result_cache.rb:92:in `save'
gems/rubocop-9cf9c3c91446/lib/rubocop/runner.rb:145:in `save_in_cache'
gems/rubocop-9cf9c3c91446/lib/rubocop/runner.rb:89:in `process_file'
gems/rubocop-9cf9c3c91446/lib/rubocop/runner.rb:59:in `block in inspect_files'
gems/rubocop-9cf9c3c91446/lib/rubocop/runner.rb:57:in `each'
gems/rubocop-9cf9c3c91446/lib/rubocop/runner.rb:57:in `inspect_files'
gems/rubocop-9cf9c3c91446/lib/rubocop/runner.rb:35:in `run'

for rubocop -C false:

C: Style/EmptyElse: Redundant else-clause.
undefined method `source_line' for #<Parser::Source::Map::Condition:0x007f7f90dd6eb0>
gems/rubocop-9cf9c3c91446/lib/rubocop/formatter/clang_style_formatter.rb:36:in `valid_line?'
gems/rubocop-9cf9c3c91446/lib/rubocop/formatter/clang_style_formatter.rb:25:in `report_offense'
gems/rubocop-9cf9c3c91446/lib/rubocop/formatter/clang_style_formatter.rb:13:in `block in report_file'
gems/rubocop-9cf9c3c91446/lib/rubocop/formatter/clang_style_formatter.rb:13:in `each'
gems/rubocop-9cf9c3c91446/lib/rubocop/formatter/clang_style_formatter.rb:13:in `report_file'
gems/rubocop-9cf9c3c91446/lib/rubocop/formatter/progress_formatter.rb:43:in `block in finished'
gems/rubocop-9cf9c3c91446/lib/rubocop/formatter/progress_formatter.rb:42:in `each'
gems/rubocop-9cf9c3c91446/lib/rubocop/formatter/progress_formatter.rb:42:in `finished'
gems/rubocop-9cf9c3c91446/lib/rubocop/formatter/formatter_set.rb:30:in `block (3 levels) in <class:FormatterSet>'
gems/rubocop-9cf9c3c91446/lib/rubocop/formatter/formatter_set.rb:30:in `each'
gems/rubocop-9cf9c3c91446/lib/rubocop/formatter/formatter_set.rb:30:in `block (2 levels) in <class:FormatterSet>'
gems/rubocop-9cf9c3c91446/lib/rubocop/runner.rb:68:in `inspect_files'
gems/rubocop-9cf9c3c91446/lib/rubocop/runner.rb:35:in `run'

---

Expected behavior

No crash

Actual behavior

Crash

Steps to reproduce the problem

run rubocop on test.rb:

def truish
  if true
    true
  else
    nil
  end
end

RuboCop version

0.40.0 (using Parser 2.3.1.2, running on ruby 2.3.1 x86_64-darwin15)