Describe the bug
I am unable to produce a changelog at all with the command github_changelog_generator -u repo-namespace -p project-name --max-issues 50, and get the below output

Found 36 tags
Fetching tags dates: 36/36
Sorting tags...
Received issues: 100
Pull Request count: 554
Filtered pull requests: 59
Filtered issues: 35
Fetching events for issues and PR: 94
Fetching closed dates for issues: 94/94
Traceback (most recent call last):
7: from /Users/emilyjablonski/.rvm/rubies/ruby-2.6.3/lib/ruby/gems/2.6.0/gems/async-1.29.0/lib/async/task.rb:263:in block in make_fiber' 6: from /Users/emilyjablonski/.rvm/rubies/ruby-2.6.3/lib/ruby/gems/2.6.0/gems/github_changelog_generator-1.16.1/lib/github_changelog_generator/generator/generator.rb:55:in block in compound_changelog'
5: from /Users/emilyjablonski/.rvm/rubies/ruby-2.6.3/lib/ruby/gems/2.6.0/gems/github_changelog_generator-1.16.1/lib/github_changelog_generator/generator/generator.rb:152:in fetch_issues_and_pr' 4: from /Users/emilyjablonski/.rvm/rubies/ruby-2.6.3/lib/ruby/gems/2.6.0/gems/github_changelog_generator-1.16.1/lib/github_changelog_generator/generator/generator_fetcher.rb:49:in add_first_occurring_tag_to_prs'
3: from /Users/emilyjablonski/.rvm/rubies/ruby-2.6.3/lib/ruby/gems/2.6.0/gems/github_changelog_generator-1.16.1/lib/github_changelog_generator/generator/generator_fetcher.rb:105:in associate_release_branch_prs' 2: from /Users/emilyjablonski/.rvm/rubies/ruby-2.6.3/lib/ruby/gems/2.6.0/gems/github_changelog_generator-1.16.1/lib/github_changelog_generator/generator/generator_fetcher.rb:105:in reject'
1: from /Users/emilyjablonski/.rvm/rubies/ruby-2.6.3/lib/ruby/gems/2.6.0/gems/github_changelog_generator-1.16.1/lib/github_changelog_generator/generator/generator_fetcher.rb:107:in block in associate_release_branch_prs' /Users/emilyjablonski/.rvm/rubies/ruby-2.6.3/lib/ruby/gems/2.6.0/gems/github_changelog_generator-1.16.1/lib/github_changelog_generator/generator/generator_fetcher.rb:201:in sha_in_release_branch': undefined method `include?' for nil:NilClass (NoMethodError)

Desktop (please complete the following information):

• OS: MacOS Catalina 10.15.7

My only thought is that this is a Ruby version issue but I just re-installed Ruby?