Lint/SymbolConversion raise undefined method `str_type?' for nil:NilClas

[ShockwaveNN]

Steps to reproduce the problem

1. Create .rubocop.yml with content:

AllCops:
    TargetRubyVersion: 2.5
    NewCops: enable

For some reason failure is not reproduces without .rubocop.yml config, not sure which line is caused it

2. Create test.rb with content:

# frozen_string_literal: true

# Class for description of horizontal alignment
class Foo
  def ==(other)
    to_sym == other if other.is_a?(Symbol)
  end
end

3. run rubocop -d test.rb will result:

rubocop -d test.rb   
For /home/lobashov/temp: configuration from /home/lobashov/temp/.rubocop.yml
Default configuration from /home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/config/default.yml
Inspecting 1 file
Scanning /home/lobashov/temp/test.rb
An error occurred while Lint/SymbolConversion cop was inspecting /home/lobashov/temp/test.rb:6:4.
undefined method `str_type?' for nil:NilClass
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cop/lint/symbol_conversion.rb:31:in `on_send'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cop/commissioner.rb:136:in `public_send'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cop/commissioner.rb:136:in `block (2 levels) in trigger_restricted_cops'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cop/commissioner.rb:166:in `with_cop_error_handling'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cop/commissioner.rb:135:in `block in trigger_restricted_cops'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cop/commissioner.rb:134:in `each'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cop/commissioner.rb:134:in `trigger_restricted_cops'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cop/commissioner.rb:70:in `on_send'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-ast-1.4.1/lib/rubocop/ast/traversal.rb:159:in `block in on_send'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-ast-1.4.1/lib/rubocop/ast/traversal.rb:156:in `each'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-ast-1.4.1/lib/rubocop/ast/traversal.rb:156:in `each_with_index'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-ast-1.4.1/lib/rubocop/ast/traversal.rb:156:in `on_send'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cop/commissioner.rb:71:in `on_send'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-ast-1.4.1/lib/rubocop/ast/traversal.rb:155:in `on_if'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cop/commissioner.rb:71:in `on_if'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-ast-1.4.1/lib/rubocop/ast/traversal.rb:154:in `on_def'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cop/commissioner.rb:71:in `on_def'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-ast-1.4.1/lib/rubocop/ast/traversal.rb:154:in `on_class'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cop/commissioner.rb:71:in `on_class'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-ast-1.4.1/lib/rubocop/ast/traversal.rb:20:in `walk'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cop/commissioner.rb:86:in `investigate'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cop/team.rb:157:in `investigate_partial'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cop/team.rb:83:in `investigate'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/runner.rb:315:in `inspect_file'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/runner.rb:259:in `block in do_inspection_loop'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/runner.rb:293:in `block in iterate_until_no_changes'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/runner.rb:286:in `loop'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/runner.rb:286:in `iterate_until_no_changes'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/runner.rb:255:in `do_inspection_loop'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/runner.rb:132:in `block in file_offenses'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/runner.rb:157:in `file_offense_cache'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/runner.rb:131:in `file_offenses'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/runner.rb:122:in `process_file'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/runner.rb:101:in `block in each_inspected_file'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/runner.rb:100:in `each'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/runner.rb:100:in `reduce'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/runner.rb:100:in `each_inspected_file'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/runner.rb:86:in `inspect_files'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/runner.rb:47:in `run'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cli/command/execute_runner.rb:26:in `block in execute_runner'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cli/command/execute_runner.rb:52:in `with_redirect'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cli/command/execute_runner.rb:25:in `execute_runner'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cli/command/execute_runner.rb:17:in `run'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cli/command.rb:11:in `run'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cli/environment.rb:18:in `run'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cli.rb:65:in `run_command'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cli.rb:72:in `execute_runners'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/lib/rubocop/cli.rb:41:in `run'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/exe/rubocop:13:in `block in <top (required)>'
/usr/share/rvm/rubies/ruby-2.7.2/lib/ruby/2.7.0/benchmark.rb:308:in `realtime'
/home/lobashov/.rvm/gems/ruby-2.7.2/gems/rubocop-1.9.0/exe/rubocop:12:in `<top (required)>'
/home/lobashov/.rvm/gems/ruby-2.7.2/bin/rubocop:23:in `load'
/home/lobashov/.rvm/gems/ruby-2.7.2/bin/rubocop:23:in `<main>'
/home/lobashov/.rvm/gems/ruby-2.7.2/bin/ruby_executable_hooks:24:in `eval'
/home/lobashov/.rvm/gems/ruby-2.7.2/bin/ruby_executable_hooks:24:in `<main>'
.

1 file inspected, no offenses detected

1 error occurred:
An error occurred while Lint/SymbolConversion cop was inspecting /home/lobashov/temp/test.rb:6:4

RuboCop version

1.9.0 (using Parser 3.0.0.0, rubocop-ast 1.4.1, running on ruby 2.7.2 x86_64-linux)