i18n_block_translate_block() uses undefined variable $localizable

i18n_block_translate_block() contains the following piece of code:

  if (!empty($block->content) && $localizable) {
    $block->content = i18n_string_text("blocks:$block->module:$block->delta:body", $block->content);
  }

The variable $localizable is not defined, meaning the conditional block will never execute.