less null: true warnings while testing against AR 4.2

Author: kares

test/db/mysql/rake_test.rb

@@ -75,7 +75,7 @@ def do_teardown
     # Rake::Task["db:create"].invoke
     create_rake_test_database do |connection|
       create_schema_migrations_table(connection)
-      connection.create_table('users') { |t| t.string :name; t.timestamps }
+      connection.create_table('users') { |t| t.string :name, :null => true; t.timestamps }
     end
 
     structure_sql = File.join('db', structure_sql_filename)