Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=1848243

Description of problem: Generating 'Applied errata' report with 'Reboot' = true and Status = warning fails with error "undefined method `uptime_seconds' for nil:NilClass"

1. hammer report-template generate --name 'Applied Errata' --inputs "Filter Errata Type = all, Include Last Reboot = yes, Status = warning"
   undefined method `uptime_seconds' for nil:NilClass

~_{~
bd089ee4-9d39-4ee1-8d91-795cd466b0d8,2,1,,skipped,2020-06-02 16:08:56.977233,2020-06-02 16:08:57.055904,0.078670509,0.064980915,1,0,Dynflow::ExecutionPlan::Steps::RunStep,{"class":"Dynflow::ExecutionPlan::Steps::Error","exception_class":"NoMethodError","message":"undefined method `uptime_seconds' for nil:NilClass","backtrace":["/opt/theforeman/tfm/root/usr/share/gems/gems/katello-3.14.0.20/app/lib/katello/concerns/base_template_scope_extensions.rb:150:in `block (3 levels) in load_errata_applications'","/opt/theforeman/tfm/root/usr/share/gems/gems/katello-3.14.0.20/app/lib/katello/concerns/base_template_scope_extensions.rb:134:in `each'","/opt/theforeman/tfm/root/usr/share/gems/gems/katello-3.14.0.20/app/lib/katello/concerns/base_template_scope_extensions.rb:134:in `block (2 levels) in load_errata_applications'","/opt/theforeman/tfm-ror52/root/usr/share/gems/gems/activerecord-5.2.1/lib/active_record/relation/delegation.rb}
~~

Version-Release number of selected component (if applicable): Satellite 6.7

Additional info:
After investigation found, If a host is deleted but task related to the host is present in the satellite.