minor improvement

app/helpers/admin/dashboard_helper.rb

@@ -5,7 +5,7 @@ module Admin
     end
 
     def docker_data
-      ExecutionEnvironment.order(:id).select(:id, :permitted_execution_time, :pool_size).map do |execution_environment|
+      ExecutionEnvironment.order(:id).select(:id, :pool_size).map do |execution_environment|
         execution_environment.attributes.merge(quantity: DockerContainerPool.quantities[execution_environment.id])
       end
     end

app/models/execution_environment.rb

@@ -19,8 +19,8 @@ class ExecutionEnvironment < ActiveRecord::Base
   validates :run_command, presence: true
 
   def set_default_values
-    self.permitted_execution_time ||= 60
-    self.pool_size ||= 0
+    self.permitted_execution_time ||= 60 if has_attribute?(:permitted_execution_time)
+    self.pool_size ||= 0 if has_attribute?(:pool_size)
   end
   private :set_default_values