Allow nil values for settings

app/models/setting_entry.rb

@@ -1,6 +1,5 @@
 class SettingEntry < ApplicationRecord
   validates :code, presence: true, uniqueness: true
-  validates :value, presence: true
   validates :format, presence: true
   validates :group, presence: true
   validate :valid_value_format
@@ -17,7 +16,7 @@ class SettingEntry < ApplicationRecord
 
   def retrieve
     method = VALUE_FORMATS[format]
-    send(method)
+    value.blank? ? nil : send(method)
   end
 
   def self.with_group(group_name)
@@ -32,7 +31,8 @@ class SettingEntry < ApplicationRecord
       stg_value = args[0].to_s
       SettingEntry.find_by!(code: stg_code).update(value: stg_value)
     else
-      SettingEntry.find_by!(code: method.to_s).retrieve
+      stg = SettingEntry.find_by(code: method.to_s)
+      stg ? stg.retrieve : nil
     end
   end
 

db/migrate/20200812090409_change_setting_entry_value_to_allow_nil.rb

@@ -0,0 +1,5 @@
+class ChangeSettingEntryValueToAllowNil < ActiveRecord::Migration[6.0]
+  def change
+    change_column :setting_entries, :value, :string, null: true
+  end
+end

db/structure.sql

@@ -2269,7 +2269,7 @@ CREATE TABLE public.schema_migrations (
 CREATE TABLE public.setting_entries (
     id bigint NOT NULL,
     code character varying NOT NULL,
-    value character varying DEFAULT ''::character varying NOT NULL,
+    value character varying DEFAULT ''::character varying,
     "group" character varying NOT NULL,
     format character varying NOT NULL,
     creator_str character varying,
@@ -4779,6 +4779,7 @@ INSERT INTO "schema_migrations" (version) VALUES
 ('20200630081231'),
 ('20200714115338'),
 ('20200807110611'),
-('20200811074839');
+('20200811074839'),
+('20200812090409');