foreman-rake katello:reimport fails in Red Hat Satellite 6 with NoMethodError: undefined method '+' for nil:NilClass

Issue

• When running foreman-rake katello:reimport hitting the following error:

  # foreman-rake katello:reimport
  /usr/share/foreman/lib/foreman.rb:8: warning: already initialized constant Foreman::UUID_REGEXP
  /usr/share/foreman/lib/foreman.rb:8: warning: previous definition of UUID_REGEXP was here
  /usr/share/foreman/lib/core_extensions.rb:182: warning: already initialized constant ActiveSupport::MessageEncryptor::DEFAULT_CIPHER
  /opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activesupport-5.1.6/lib/active_support/message_encryptor.rb:22: warning: previous definition of DEFAULT_CIPHER was here
  Importing Katello::Erratum
  Importing Katello::PackageGroup
  Importing Katello::PuppetModule
  Importing Katello::Rpm
  Importing Katello::Srpm
  Importing Katello::Deb
  Importing Katello::FileUnit
  Importing Katello::Subscription
  Importing Katello::Pool
  Importing Katello::DockerManifest
  Importing Katello::DockerManifestList
  Importing Katello::DockerTag
  Importing Katello::ContentViewPuppetEnvironment
  Importing Katello::Content
  rake aborted!
  NoMethodError: undefined method '+' for nil:NilClass
  /opt/theforeman/tfm/root/usr/share/gems/gems/katello-3.7.0.41/app/lib/katello/resources/candlepin/product.rb:25:in 'get'
  /opt/theforeman/tfm/root/usr/share/gems/gems/katello-3.7.0.41/app/models/katello/content.rb:40:in `block (2 levels) in import_all'
  /opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/relation/delegation.rb:39:in 'each'
  /opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/relation/delegation.rb:39:in 'each'
  /opt/theforeman/tfm/root/usr/share/gems/gems/katello-3.7.0.41/app/models/katello/content.rb:38:in 'block in import_all'
  /opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/relation/delegation.rb:39:in `each'
  /opt/theforeman/tfm-ror51/root/usr/share/gems/gems/activerecord-5.1.6/lib/active_record/relation/delegation.rb:39:in `each'
  /opt/theforeman/tfm/root/usr/share/gems/gems/katello-3.7.0.41/app/models/katello/content.rb:37:in `import_all'
  /opt/theforeman/tfm/root/usr/share/gems/gems/katello-3.7.0.41/lib/katello/tasks/reimport.rake:39:in `block (3 levels) in top (required)'
  /opt/theforeman/tfm/root/usr/share/gems/gems/katello-3.7.0.41/lib/katello/tasks/reimport.rake:37:in `each'
  /opt/theforeman/tfm/root/usr/share/gems/gems/katello-3.7.0.41/lib/katello/tasks/reimport.rake:37:in `block (2 levels) in top (required)'
  /opt/rh/rh-ruby24/root/usr/share/gems/gems/rake-12.0.0/exe/rake:27:in `top (required)'
  Tasks: TOP => katello:reimport
  (See full trace by running task with --trace)