undefined method `next_time' for nil:NilClass (#445)

[mauricebolhuis]

Sidekiq-scheduler allows to schedule jobs using different schedule types. One of the schedule types is at, that pushes jobs only once and schedules it in a single point in time. Defining a job in sidekiq.yml with an at schedule type and a date in the past resulted in an error and prevented Sidekiq from starting:

11:36:07 sidekiq.1 | 2024-05-01T09:36:07.190Z pid=515927 tid=axvj INFO: Scheduling foo {"class"=>"FooJob", "at"=>"2024/04/30", "enabled"=>false, "queue"=>"default"}
11:36:07 sidekiq.1 | 2024-05-01T09:36:07.191Z pid=515927 tid=axvj WARN: {"context":"Exception during Sidekiq lifecycle event.","event":"startup"}
11:36:07 sidekiq.1 | 2024-05-01T09:36:07.191Z pid=515927 tid=axvj WARN: NoMethodError: undefined method `next_time' for nil
11:36:07 sidekiq.1 | 2024-05-01T09:36:07.191Z pid=515927 tid=axvj WARN: 
11:36:07 sidekiq.1 | undefined method `next_time' for nil
11:36:07 sidekiq.1 | /home/maurice/.rbenv/versions/3.3.0/lib/ruby/gems/3.3.0/gems/sidekiq-scheduler-5.0.3/lib/sidekiq-scheduler/scheduler.rb:133:in `block in load_schedule_job'
11:36:07 sidekiq.1 | /home/maurice/.rbenv/versions/3.3.0/lib/ruby/gems/3.3.0/gems/sidekiq-scheduler-5.0.3/lib/sidekiq-scheduler/scheduler.rb:123:in `each'
11:36:07 sidekiq.1 | /home/maurice/.rbenv/versions/3.3.0/lib/ruby/gems/3.3.0/gems/sidekiq-scheduler-5.0.3/lib/sidekiq-scheduler/scheduler.rb:123:in `load_schedule_job'
11:36:07 sidekiq.1 | /home/maurice/.rbenv/versions/3.3.0/lib/ruby/gems/3.3.0/gems/sidekiq-scheduler-5.0.3/lib/sidekiq-scheduler/scheduler.rb:101:in `block in load_schedule!'
11:36:07 sidekiq.1 | /home/maurice/.rbenv/versions/3.3.0/lib/ruby/gems/3.3.0/gems/sidekiq-scheduler-5.0.3/lib/sidekiq-scheduler/scheduler.rb:99:in `each'
11:36:07 sidekiq.1 | /home/maurice/.rbenv/versions/3.3.0/lib/ruby/gems/3.3.0/gems/sidekiq-scheduler-5.0.3/lib/sidekiq-scheduler/scheduler.rb:99:in `load_schedule!'
11:36:07 sidekiq.1 | /home/maurice/.rbenv/versions/3.3.0/lib/ruby/gems/3.3.0/gems/sidekiq-scheduler-5.0.3/lib/sidekiq-scheduler/manager.rb:24:in `start'
11:36:07 sidekiq.1 | /home/maurice/.rbenv/versions/3.3.0/lib/ruby/gems/3.3.0/gems/sidekiq-scheduler-5.0.3/lib/sidekiq-scheduler/sidekiq_adapter.rb:41:in `start_schedule_manager'
11:36:07 sidekiq.1 | /home/maurice/.rbenv/versions/3.3.0/lib/ruby/gems/3.3.0/gems/sidekiq-scheduler-5.0.3/lib/sidekiq-scheduler.rb:21:in `block (2 levels) in <main>'

When the date of an at scheduled job is in the past, it does not have to schedule the job another time. This PR fixes this by skipping to set the job next_time.

[marcelolx]

Thanks @mauricebolhuis