update migrations

db/migrate/20181114180205_change_descendant_names_to_array_on_tag_implications.rb

@@ -1,6 +1,7 @@
 class ChangeDescendantNamesToArrayOnTagImplications < ActiveRecord::Migration[5.2]
   def up
     TagImplication.without_timeout do
+      change_column_default :tag_implications, :descendant_names, from: '', to: false
       change_column :tag_implications, :descendant_names, "text[]", using: "string_to_array(descendant_names, ' ')::text[]", default: "{}"
     end
   end

db/migrate/20181114185032_change_strings_to_arrays_on_artist_versions.rb

@@ -1,6 +1,7 @@
 class ChangeStringsToArraysOnArtistVersions < ActiveRecord::Migration[5.2]
   def up
     ArtistVersion.without_timeout do
+      change_column_default :artist_versions, :other_names, from: '', to: false
       change_column :artist_versions, :other_names, "text[]", using: "array_remove(regexp_split_to_array(other_names, '\\s+'), '')", default: "{}"
 
       change_column :artist_versions, :url_string, "text[]", using: "array_remove(regexp_split_to_array(url_string, '\\s+'), '')", default: "{}"

db/migrate/20181114202744_change_other_names_to_array_on_artists.rb

@@ -1,6 +1,7 @@
 class ChangeOtherNamesToArrayOnArtists < ActiveRecord::Migration[5.2]
   def up
     Artist.without_timeout do
+      change_column_default :artists, :other_names, from: '', to: false
       remove_index :artists, name: "index_artists_on_other_names_trgm"
       change_column :artists, :other_names, "text[]", using: "array_remove(regexp_split_to_array(other_names, '\\s+'), '')", default: "{}"
       add_index :artists, :other_names, using: :gin