emit_warning_if_null_unspecified

# File activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb, line 60
      def emit_warning_if_null_unspecified(sym, options)
        return if options.key?(:null)

        ActiveSupport::Deprecation.warn(          `##{sym}` was called without specifying an option for `null`. In Rails 5,          this behavior will change to `null: false`. You should manually specify         `null: true` to prevent the behavior of your existing migrations from changing..squish)
      end