diff --git a/app/models/exercise_collection.rb b/app/models/exercise_collection.rb index 661bed81..5c159dda 100644 --- a/app/models/exercise_collection.rb +++ b/app/models/exercise_collection.rb @@ -13,7 +13,12 @@ class ExerciseCollection < ActiveRecord::Base end def average_working_time - exercise_working_times.values.reduce(:+) / exercises.size + if exercises.empty? + 0 + else + values = exercise_working_times.values.reject { |v| v.nil?} + values.reduce(:+) / exercises.size + end end def to_s