0.38.0: Style/Next autocorrection breaks files without Style/MultilineIfThen

[dabroz]

I know, this is quite a corner case. However I found that Style/Next autocorrection can break valid Ruby files unless Style/MultilineIfThen is also enabled.

Test case

# rubocop:disable Style/MultilineIfThen

[].each do |a|
  if a then
    puts
    puts
    puts
  end
end

Expected behavior

Either file doesn't get modified, or invalid then is removed during the transformation.

Actual behavior

[].each do |a|
  next unless a then
  puts
  puts
  puts
end

(which is invalid Ruby code)

Steps to reproduce the problem

1. Put test case in a test.rb file
2. Run rubocop -a

RuboCop version

0.38.0 (using Parser 2.3.0.6, running on ruby 2.2.4 x86_64-darwin14)