Handle Enumerable methods called with no receiver in CollectionLiteralInLoop

[eugeneius]

The test added here demonstrates the problem:

$ bundle exec rspec spec/rubocop/cop/performance/collection_literal_in_loop_spec.rb:149
Run options: include {:locations=>{"./spec/rubocop/cop/performance/collection_literal_in_loop_spec.rb"=>[149]}}

Randomized with seed 21526

RuboCop::Cop::Performance::CollectionLiteralInLoop
  when inside one of `Enumerable` loop-like methods
    registers an offense when the method is called with no receiver (FAILED - 1)

Failures:

  1) RuboCop::Cop::Performance::CollectionLiteralInLoop when inside one of `Enumerable` loop-like methods registers an offense when the method is called with no receiver
     Failure/Error: receiver != node && !receiver.descendants.include?(node)

     NoMethodError:
       undefined method `descendants' for nil:NilClass
     # ./lib/rubocop/cop/performance/collection_literal_in_loop.rb:118:in `block in node_within_enumerable_loop?'
     # ./lib/rubocop/cop/performance/collection_literal_in_loop.rb:85:in `enumerable_loop?'
     # ./lib/rubocop/cop/performance/collection_literal_in_loop.rb:117:in `node_within_enumerable_loop?'
     # ./lib/rubocop/cop/performance/collection_literal_in_loop.rb:109:in `loop?'
     # ./lib/rubocop/cop/performance/collection_literal_in_loop.rb:103:in `block in parent_is_loop?'
     # ./lib/rubocop/cop/performance/collection_literal_in_loop.rb:103:in `each'
     # ./lib/rubocop/cop/performance/collection_literal_in_loop.rb:103:in `any?'
     # ./lib/rubocop/cop/performance/collection_literal_in_loop.rb:103:in `parent_is_loop?'
     # ./lib/rubocop/cop/performance/collection_literal_in_loop.rb:82:in `on_send'
     # ./spec/rubocop/cop/performance/collection_literal_in_loop_spec.rb:150:in `block (3 levels) in <top (required)>'

Finished in 0.03141 seconds (files took 0.8423 seconds to load)
1 example, 1 failure

Failed examples:

rspec ./spec/rubocop/cop/performance/collection_literal_in_loop_spec.rb:149 # RuboCop::Cop::Performance::CollectionLiteralInLoop when inside one of `Enumerable` loop-like methods registers an offense when the method is called with no receiver

Randomized with seed 21526

---

Before submitting the PR make sure the following are checked:

• 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.

[koic]

Thanks!