Fix a false positive for Layout/EmptyLinesAroundAttributeAccessor

[koic]

This PR fixes the following false positive for Layout/EmptyLinesAroundAttributeAccessor when using attribute accessors in if ... else branches.

if condition
  attr_reader :foo
else
  do_something
end

% bundle exec rubocop --only Layout/EmptyLinesAroundAttributeAccessor
(snip)
Inspecting 1 file
C

Offenses:

example.rb:2:3: C: Layout/EmptyLinesAroundAttributeAccessor: Add an
empty line after attribute accessor.
  attr_reader :foo
  ^^^^^^^^^^^^^^^^

1 file inspected, 1 offense detected

---

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• 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.
• Added an entry to the Changelog if the new code introduces user-observable changes. See changelog entry format.
• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Run bundle exec rake default. It executes all tests and RuboCop for itself, and generates the documentation.

[bbatsov]

Looks good!