Previously if when node has an empty body this cop raises:

case 1
when 1 # no body
  # 1 == 1
else
  nil
end

undefined method `loc' for nil
    # ./lib/rubocop/cop/performance/case_when_splat.rb:154:in `indent_for'
    # ./lib/rubocop/cop/performance/case_when_splat.rb:144:in `new_branch_without_then'
    # ./lib/rubocop/cop/performance/case_when_splat.rb:123:in `reordering_correction'
    # ./lib/rubocop/cop/performance/case_when_splat.rb:114:in `reorder_condition'
    # ./lib/rubocop/cop/performance/case_when_splat.rb:86:in `autocorrect'

It also did not preserve comments.

Before submitting the PR make sure the following are checked:

• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• Added an entry (file) to the changelog folder named {change_type}_{change_description}.md if the new code introduces user-observable changes. See changelog entry format for details.