IssueActions checks user permissions when there's no user

https://sentry.gitlab.net/gitlab/gitlabcom/issues/1074904/

NoMethodError: undefined method `can?' for nil:NilClass
  gitlab/quick_actions/issue_actions.rb:22:in `block (2 levels) in <module:IssueActions>'
    current_user.can?(:"admin_#{quick_action_target.to_ability_name}", project)
  gitlab/quick_actions/command_definition.rb:36:in `instance_exec'
    context.instance_exec(&condition_block)
  gitlab/quick_actions/command_definition.rb:36:in `available?'
    context.instance_exec(&condition_block)
  quick_actions/interpret_service.rb:27:in `block in available_commands'
    next unless definition.available?(self)
  quick_actions/interpret_service.rb:26:in `map'
    self.class.command_definitions.map do |definition|
...
(131 additional frame(s) were not displayed)

NoMethodError: undefined method `can?' for nil:NilClass