Error in Rubocop 0.50.0's Style/SafeNavigation cop

.rubocop.yml

AllCops:
  TargetRubyVersion: 2.4

_README.md

Reproduce

1. Clone gist:

    $ git clone git@gist.github.com:c65abfdd6e2bf36dcadc9b5364a0b741.git rubocop-style-safe-naviation-error
    $ cd rubocop-style-safe-naviation-error
   

2. Bundle install:

    $ bundle install
   

3. Run Rubocop:

    $ bundle exec rubocop
    Inspecting 2 files
    C.
   
    Offenses:
   
    foobar.rb:3:1: C: Use safe navigation (&.) instead of checking if an object exists before calling the method.
    foo[bar] if foo
    ^^^^^^^^^^^^^^^
   
    2 files inspected, 1 offense detected
   

4. Run Rubocop auto-correct:

    $ bundle exec rubocop --auto-correct
    Inspecting 2 files
   
    0 files inspected, no offenses detected
    undefined method `begin' for nil:NilClass
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/parser-2.4.0.0/lib/parser/source/rewriter.rb:67:in `insert_before'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/cop/corrector.rb:78:in `insert_before'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/cop/style/safe_navigation.rb:99:in `block in autocorrect'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/cop/corrector.rb:56:in `block (2 levels) in rewrite'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/parser-2.4.0.0/lib/parser/source/rewriter.rb:194:in `transaction'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/cop/corrector.rb:55:in `block in rewrite'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/cop/corrector.rb:53:in `each'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/cop/corrector.rb:53:in `rewrite'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/cop/team.rb:126:in `autocorrect_all_cops'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/cop/team.rb:70:in `autocorrect'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/cop/team.rb:98:in `block in offenses'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/cop/team.rb:115:in `investigate'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/cop/team.rb:94:in `offenses'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/cop/team.rb:44:in `inspect_file'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/runner.rb:258:in `inspect_file'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/runner.rb:205:in `block in do_inspection_loop'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/runner.rb:237:in `block in iterate_until_no_changes'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/runner.rb:230:in `loop'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/runner.rb:230:in `iterate_until_no_changes'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/runner.rb:201:in `do_inspection_loop'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/runner.rb:111:in `block in file_offenses'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/runner.rb:121:in `file_offense_cache'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/runner.rb:109:in `file_offenses'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/runner.rb:100:in `process_file'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/runner.rb:78:in `block in each_inspected_file'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/runner.rb:75:in `each'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/runner.rb:75:in `reduce'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/runner.rb:75:in `each_inspected_file'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/runner.rb:67:in `inspect_files'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/runner.rb:39:in `run'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/cli.rb:86:in `execute_runner'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/lib/rubocop/cli.rb:32:in `run'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/bin/rubocop:13:in `block in <top (required)>'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/2.4.0/benchmark.rb:308:in `realtime'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rubocop-0.50.0/bin/rubocop:12:in `<top (required)>'
    /Users/jimeh/.rbenv/versions/2.4.1/bin/rubocop:22:in `load'
    /Users/jimeh/.rbenv/versions/2.4.1/bin/rubocop:22:in `<top (required)>'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/bundler-1.15.4/lib/bundler/cli/exec.rb:74:in `load'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/bundler-1.15.4/lib/bundler/cli/exec.rb:74:in `kernel_load'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/bundler-1.15.4/lib/bundler/cli/exec.rb:27:in `run'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/bundler-1.15.4/lib/bundler/cli.rb:362:in `exec'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/bundler-1.15.4/lib/bundler/vendor/thor/lib/thor/command.rb:27:in `run'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/bundler-1.15.4/lib/bundler/vendor/thor/lib/thor/invocation.rb:126:in `invoke_command'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/bundler-1.15.4/lib/bundler/vendor/thor/lib/thor.rb:387:in `dispatch'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/bundler-1.15.4/lib/bundler/cli.rb:22:in `dispatch'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/bundler-1.15.4/lib/bundler/vendor/thor/lib/thor/base.rb:466:in `start'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/bundler-1.15.4/lib/bundler/cli.rb:13:in `start'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/bundler-1.15.4/exe/bundle:30:in `block in <top (required)>'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/bundler-1.15.4/lib/bundler/friendly_errors.rb:121:in `with_friendly_errors'
    /Users/jimeh/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/bundler-1.15.4/exe/bundle:22:in `<top (required)>'
    /Users/jimeh/.rbenv/versions/2.4.1/bin/bundle:22:in `load'
    /Users/jimeh/.rbenv/versions/2.4.1/bin/bundle:22:in `<main>'
   

foobar.rb

# frozen_string_literal: true

foo[bar] if foo

Gemfile

# frozen_string_literal: true

source 'https://rubygems.org/'

gem 'rubocop', '0.50.0'

Gemfile.lock

GEM
  remote: https://rubygems.org/
  specs:
    ast (2.3.0)
    parallel (1.12.0)
    parser (2.4.0.0)
      ast (~> 2.2)
    powerpack (0.1.1)
    rainbow (2.2.2)
      rake
    rake (12.1.0)
    rubocop (0.50.0)
      parallel (~> 1.10)
      parser (>= 2.3.3.1, < 3.0)
      powerpack (~> 0.1)
      rainbow (>= 2.2.2, < 3.0)
      ruby-progressbar (~> 1.7)
      unicode-display_width (~> 1.0, >= 1.0.1)
    ruby-progressbar (1.8.3)
    unicode-display_width (1.3.0)

PLATFORMS
  ruby

DEPENDENCIES
  rubocop (= 0.50.0)

BUNDLED WITH
   1.15.4