add_apszhp_to_each_zone should fail on nil as well

[corymosiman12]

https://github.com/NREL/openstudio-ee-gem/blob/5b15fa1b9dad2994209f25d80d0dd6b31a02ee44/lib/measures/add_apszhp_to_each_zone/measure.rb#L212

================ ZONES THAT MATCHED THE FILTER ================ [14:01:13.077073 ERROR] undefined method `each' for nil:NilClass /Users/cmosiman/Github/BuildingSync/BuildingSync-gem/.bundle/install/ruby/2.5.0/bundler/gems/openstudio-ee-gem-4d47e51086df/lib/measures/add_apszhp_to_each_zone/measure.rb:221:in `run'