Liquid Exception: undefined method `[]' for nil:NilClass in office/us-president/index.md

bundle exec jekyll build --trace

Liquid Exception: undefined method `[]' for nil:NilClass in office/us-president/index.md
bundler: failed to load command: jekyll (/Users/trobbins/.gem/ruby/2.6.0/bin/jekyll)
NoMethodError: undefined method `[]' for nil:NilClass
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/filters.rb:323:in `block in item_property'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/filters.rb:322:in `each'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/filters.rb:322:in `reduce'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/filters.rb:322:in `item_property'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/filters.rb:184:in `block in where'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/filters.rb:183:in `select'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/filters.rb:183:in `where'
  /Users/trobbins/.gem/ruby/2.6.0/gems/liquid-4.0.3/lib/liquid/strainer.rb:56:in `invoke'
  /Users/trobbins/.gem/ruby/2.6.0/gems/liquid-4.0.3/lib/liquid/context.rb:86:in `invoke'
  /Users/trobbins/.gem/ruby/2.6.0/gems/liquid-4.0.3/lib/liquid/variable.rb:84:in `block in render'
  /Users/trobbins/.gem/ruby/2.6.0/gems/liquid-4.0.3/lib/liquid/variable.rb:82:in `each'
  /Users/trobbins/.gem/ruby/2.6.0/gems/liquid-4.0.3/lib/liquid/variable.rb:82:in `inject'
  /Users/trobbins/.gem/ruby/2.6.0/gems/liquid-4.0.3/lib/liquid/variable.rb:82:in `render'
  /Users/trobbins/.gem/ruby/2.6.0/gems/liquid-4.0.3/lib/liquid/tags/assign.rb:26:in `render'
  /Users/trobbins/.gem/ruby/2.6.0/gems/liquid-4.0.3/lib/liquid/block_body.rb:103:in `render_node_to_output'
  /Users/trobbins/.gem/ruby/2.6.0/gems/liquid-4.0.3/lib/liquid/block_body.rb:91:in `render'
  /Users/trobbins/.gem/ruby/2.6.0/gems/liquid-4.0.3/lib/liquid/template.rb:208:in `block in render'
  /Users/trobbins/.gem/ruby/2.6.0/gems/liquid-4.0.3/lib/liquid/template.rb:242:in `with_profiling'
  /Users/trobbins/.gem/ruby/2.6.0/gems/liquid-4.0.3/lib/liquid/template.rb:207:in `render'
  /Users/trobbins/.gem/ruby/2.6.0/gems/liquid-4.0.3/lib/liquid/template.rb:220:in `render!'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/liquid_renderer/file.rb:30:in `block (2 levels) in render!'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/liquid_renderer/file.rb:42:in `measure_bytes'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/liquid_renderer/file.rb:29:in `block in render!'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/liquid_renderer/file.rb:49:in `measure_time'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/liquid_renderer/file.rb:28:in `render!'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/renderer.rb:126:in `render_liquid'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/renderer.rb:79:in `render_document'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/renderer.rb:62:in `run'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/site.rb:479:in `render_regenerated'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/site.rb:472:in `block in render_pages'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/site.rb:471:in `each'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/site.rb:471:in `render_pages'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/site.rb:192:in `render'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/site.rb:71:in `process'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/command.rb:28:in `process_site'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/commands/build.rb:65:in `build'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/commands/build.rb:36:in `process'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/lib/jekyll/commands/build.rb:18:in `block (2 levels) in init_with_program'
  /Users/trobbins/.gem/ruby/2.6.0/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `block in execute'
  /Users/trobbins/.gem/ruby/2.6.0/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `each'
  /Users/trobbins/.gem/ruby/2.6.0/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `execute'
  /Users/trobbins/.gem/ruby/2.6.0/gems/mercenary-0.3.6/lib/mercenary/program.rb:42:in `go'
  /Users/trobbins/.gem/ruby/2.6.0/gems/mercenary-0.3.6/lib/mercenary.rb:19:in `program'
  /Library/Ruby/Gems/2.6.0/gems/jekyll-3.8.5/exe/jekyll:15:in `<top (required)>'
  /Users/trobbins/.gem/ruby/2.6.0/bin/jekyll:23:in `load'
  /Users/trobbins/.gem/ruby/2.6.0/bin/jekyll:23:in `<top (required)>'