project_was_not_exported_email_text_erb: undefined local variable or method `error'

/cc: @jameslopez

https://sentry.gitlap.com/gitlab/gitlabcom/issues/7748/

NameError: undefined local variable or method `error' for #<#<Class:0x00000006d60820>:0x000000103d5ff8>
  app/views/notify/project_was_not_exported_email.text.erb:6:in `_app_views_notify_project_was_not_exported_email_text_erb___390047256493390174_145687320'
    <%= error %>
  app/mailers/emails/projects.rb:21:in `project_was_not_exported_email'
    mail(to: current_user.notification_email,
  lib/gitlab/metrics/instrumentation.rb:152:in `block in project_was_not_exported_email'
    trans.measure_method(#{label.inspect}) { super }
  lib/gitlab/metrics/method_call.rb:23:in `measure'
    retval = yield
  lib/gitlab/metrics/transaction.rb:71:in `measure_method'
    @methods[name].measure(&block)
...
(120 additional frame(s) were not displayed)

ActionView::Template::Error: undefined local variable or method `error' for #<#<Class:0x00000006d60820>:0x000000103d5ff8>
  app/views/notify/project_was_not_exported_email.text.erb:6:in `_app_views_notify_project_was_not_exported_email_text_erb___390047256493390174_145687320'
    <%= error %>
  app/mailers/emails/projects.rb:21:in `project_was_not_exported_email'
    mail(to: current_user.notification_email,
  lib/gitlab/metrics/instrumentation.rb:152:in `block in project_was_not_exported_email'
    trans.measure_method(#{label.inspect}) { super }
  lib/gitlab/metrics/method_call.rb:23:in `measure'
    retval = yield
  lib/gitlab/metrics/transaction.rb:71:in `measure_method'
    @methods[name].measure(&block)
...
(120 additional frame(s) were not displayed)