suggested changes

db/migrate/20170529215453_create_organizations.rb

@@ -1,7 +1,7 @@
 class CreateOrganizations < ActiveRecord::Migration
   def change
     create_table :organizations do |t|
-      t.string :name
+      t.string :name, null: false
       t.text :description
       t.string :picture
     end

db/migrate/20170531094819_move_conferences_to_organizations.rb

@@ -8,14 +8,15 @@ class MoveConferencesToOrganizations < ActiveRecord::Migration
   end
 
   def change
-    add_reference :conferences, :organization, index: true
-    add_foreign_key :conferences, :organizations, dependent: :delete
+    add_reference :conferences, :organization, index: true, foreign_key: true
 
     TempConference.reset_column_information
-    organization = TempOrganization.create(name: 'organization', description: 'Default organization to migrate old conferences to the new version of OSEM')
-    TempConference.all.each do |conference|
-      conference.organization_id = organization.id
-      conference.save!
+    if TempConference.count != 0
+      organization = TempOrganization.create(name: 'organization', description: 'Default organization')
+      TempConference.all.each do |conference|
+        conference.organization_id = organization.id
+        conference.save!
+      end
     end
   end
 end

db/schema.rb

@@ -270,7 +270,7 @@ ActiveRecord::Schema.define(version: 20170531094819) do
   end
 
   create_table "organizations", force: :cascade do |t|
-    t.string "name"
+    t.string "name",        null: false
     t.text   "description"
     t.string "picture"
   end