TestFileName errors when encountering files without classes

[coding-chimp]

After updating to v0.26.0, I'm seeing errors like these in a gem I'm working on:

An error occurred while Minitest/TestFileName cop was inspecting PATH_TO_GEM/test/dummy/config/initializers/content_security_policy.rb.
An error occurred while Minitest/TestFileName cop was inspecting PATH_TO_GEM/test/dummy/config/initializers/inflections.rb.
An error occurred while Minitest/TestFileName cop was inspecting PATH_TO_GEM/test/dummy/config/initializers/permissions_policy.rb.

Those files are part of a dummy Rails application we use for testing. They mainly contain comments.

This is the backtrace I'm getting when running rubocop -d:

undefined method `class_type?' for nil:NilClass
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-minitest-0.26.0/lib/rubocop/cop/minitest/test_file_name.rb:32:in `test_file?'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-minitest-0.26.0/lib/rubocop/cop/minitest/test_file_name.rb:24:in `on_new_investigation'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cop/commissioner.rb:154:in `block (2 levels) in invoke'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cop/commissioner.rb:165:in `with_cop_error_handling'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cop/commissioner.rb:154:in `block in invoke'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cop/commissioner.rb:154:in `each'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cop/commissioner.rb:154:in `invoke'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cop/commissioner.rb:84:in `investigate'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cop/team.rb:154:in `investigate_partial'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cop/team.rb:97:in `investigate'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/runner.rb:322:in `inspect_file'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/runner.rb:266:in `block in do_inspection_loop'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/runner.rb:300:in `block in iterate_until_no_changes'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/runner.rb:293:in `loop'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/runner.rb:293:in `iterate_until_no_changes'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/runner.rb:262:in `do_inspection_loop'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/runner.rb:143:in `block in file_offenses'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/runner.rb:168:in `file_offense_cache'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/runner.rb:142:in `file_offenses'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/runner.rb:133:in `process_file'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/runner.rb:114:in `block in each_inspected_file'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/runner.rb:113:in `each'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/runner.rb:113:in `reduce'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/runner.rb:113:in `each_inspected_file'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/runner.rb:99:in `inspect_files'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/runner.rb:52:in `run'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cli/command/execute_runner.rb:26:in `block in execute_runner'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cli/command/execute_runner.rb:52:in `with_redirect'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cli/command/execute_runner.rb:25:in `execute_runner'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cli/command/execute_runner.rb:17:in `run'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cli/command.rb:11:in `run'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cli/environment.rb:18:in `run'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cli.rb:72:in `run_command'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cli.rb:79:in `execute_runners'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/lib/rubocop/cli.rb:48:in `run'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/exe/rubocop:19:in `block in <top (required)>'
/opt/rubies/3.2.0/lib/ruby/3.2.0/benchmark.rb:311:in `realtime'
/Users/codechimp/.gem/ruby/3.2.0/gems/rubocop-1.43.0/exe/rubocop:19:in `<top (required)>'
/Users/codechimp/.gem/ruby/3.2.0/bin/rubocop:25:in `load'
/Users/codechimp/.gem/ruby/3.2.0/bin/rubocop:25:in `<top (required)>'
/Users/codechimp/.gem/ruby/3.2.0/gems/bundler-2.3.5/lib/bundler/cli/exec.rb:58:in `load'
/Users/codechimp/.gem/ruby/3.2.0/gems/bundler-2.3.5/lib/bundler/cli/exec.rb:58:in `kernel_load'
/Users/codechimp/.gem/ruby/3.2.0/gems/bundler-2.3.5/lib/bundler/cli/exec.rb:23:in `run'
/Users/codechimp/.gem/ruby/3.2.0/gems/bundler-2.3.5/lib/bundler/cli.rb:484:in `exec'
/Users/codechimp/.gem/ruby/3.2.0/gems/bundler-2.3.5/lib/bundler/vendor/thor/lib/thor/command.rb:27:in `run'
/Users/codechimp/.gem/ruby/3.2.0/gems/bundler-2.3.5/lib/bundler/vendor/thor/lib/thor/invocation.rb:127:in `invoke_command'
/Users/codechimp/.gem/ruby/3.2.0/gems/bundler-2.3.5/lib/bundler/vendor/thor/lib/thor.rb:392:in `dispatch'
/Users/codechimp/.gem/ruby/3.2.0/gems/bundler-2.3.5/lib/bundler/cli.rb:31:in `dispatch'
/Users/codechimp/.gem/ruby/3.2.0/gems/bundler-2.3.5/lib/bundler/vendor/thor/lib/thor/base.rb:485:in `start'
/Users/codechimp/.gem/ruby/3.2.0/gems/bundler-2.3.5/lib/bundler/cli.rb:25:in `start'
/Users/codechimp/.gem/ruby/3.2.0/gems/bundler-2.3.5/exe/bundle:48:in `block in <top (required)>'
/Users/codechimp/.gem/ruby/3.2.0/gems/bundler-2.3.5/lib/bundler/friendly_errors.rb:103:in `with_friendly_errors'
/Users/codechimp/.gem/ruby/3.2.0/gems/bundler-2.3.5/exe/bundle:36:in `<top (required)>'
/Users/codechimp/.gem/ruby/3.2.0/bin/bundle:25:in `load'
/Users/codechimp/.gem/ruby/3.2.0/bin/bundle:25:in `<main>'

---

Expected behavior

The TestFileName cop should run without errors and not register any offenses for empty files.

Actual behavior

The TestFileName cop errors.

Steps to reproduce the problem

Add an empty file to the test directory.

RuboCop version

> rubocop -V                                                                                                                                                                                                                                                       3.2.0 dependabot/bundler/rubocop-minitest-0.26.0@b7f1008 ✗
1.43.0 (using Parser 3.2.0.0, rubocop-ast 1.24.1, running on ruby 3.2.0) [arm64-darwin21.5.0]
  - rubocop-minitest 0.26.0
  - rubocop-rake 0.6.0