Set visibility field default to null

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

priv/repo/migrations/20190130151607_split_event_visibility_and_join_options.exs

@@ -5,6 +5,8 @@ defmodule Mobilizon.Repo.Migrations.SplitEventVisibilityAndJoinOptions do
 
   @doc """
   EventVisibilityEnum has dropped some possible values, so we need to recreate it
+
+  Visibility allowed nullable values previously
   """
   def up do
     execute "ALTER TABLE events ALTER COLUMN visibility TYPE VARCHAR USING visibility::text"
@@ -16,6 +18,12 @@ defmodule Mobilizon.Repo.Migrations.SplitEventVisibilityAndJoinOptions do
     alter table(:events) do
       add(:join_options, JoinOptionsEnum.type(), null: false, default: "free")
     end
+
+    execute "UPDATE events SET visibility = 'public' WHERE visibility IS NULL"
+
+    alter table(:events) do
+      modify(:visibility, EventVisibilityEnum.type(), null: false, default: "public")
+    end
   end
 
   def down do