Deleted threads with deadlines

[nikolai-b]

When a thread is deleted with a deadline message we still try to email about it, which fails.

rake aborted!
NoMethodError: undefined method `email_subscribers' for nil:NilClass
/var/www/cyclescape/releases/c4a19003453e0605f109fd247b1149781a8fa2c5/app/models/messages/deadline_message.rb:15:in `block in email_upcomming_deadlines!'
/var/www/cyclescape/shared/bundle/ruby/2.5.0/gems/activerecord-5.2.4.2/lib/active_record/relation/batches.rb:70:in `block (2 levels) in find_each'
/var/www/cyclescape/shared/bundle/ruby/2.5.0/gems/activerecord-5.2.4.2/lib/active_record/relation/batches.rb:70:in `each'
/var/www/cyclescape/shared/bundle/ruby/2.5.0/gems/activerecord-5.2.4.2/lib/active_record/relation/batches.rb:70:in `block in find_each'
/var/www/cyclescape/shared/bundle/ruby/2.5.0/gems/activerecord-5.2.4.2/lib/active_record/relation/batches.rb:136:in `block in find_in_batches'
/var/www/cyclescape/shared/bundle/ruby/2.5.0/gems/activerecord-5.2.4.2/lib/active_record/relation/batches.rb:238:in `block in in_batches'
/var/www/cyclescape/shared/bundle/ruby/2.5.0/gems/activerecord-5.2.4.2/lib/active_record/relation/batches.rb:222:in `loop'
/var/www/cyclescape/shared/bundle/ruby/2.5.0/gems/activerecord-5.2.4.2/lib/active_record/relation/batches.rb:222:in `in_batches'
/var/www/cyclescape/shared/bundle/ruby/2.5.0/gems/activerecord-5.2.4.2/lib/active_record/relation/batches.rb:135:in `find_in_batches'
/var/www/cyclescape/shared/bundle/ruby/2.5.0/gems/activerecord-5.2.4.2/lib/active_record/relation/batches.rb:69:in `find_each'
/var/www/cyclescape/releases/c4a19003453e0605f109fd247b1149781a8fa2c5/app/models/messages/deadline_message.rb:13:in `email_upcomming_deadlines!'
/var/www/cyclescape/releases/c4a19003453e0605f109fd247b1149781a8fa2c5/lib/tasks/scheduled.rake:23:in `block (2 levels) in <top (required)>'
/var/www/cyclescape/shared/bundle/ruby/2.5.0/gems/rake-12.3.3/exe/rake:27:in `<top (required)>'
Tasks: TOP => scheduled:upcoming_deadlines