incorrect checking of DB query return

  // Update scheduler record.
  $query = db_merge('simplenews_scheduler');
  $query->key(array(
      'nid' => $nid,
    ))
    ->fields($record)
    ->execute();

  if (!$query) {
    drupal_set_message(t('Saving or updating schedule settings for <em>@title</em> has been unsuccessful.', array(
        '@title' => $node->title,
      )), 'error');
  }
  else {
    drupal_set_message(t('Newsletter Schedule preferences have been saved.'));
  }

If I'm reading this correctly, then we'll never fail the if(). $query will always be a query object. What we seem to be trying to do here is check what execute() returns -- which appears not to be documented, see #1479220: Add return documentation for Merge::execute() -- and show a message based on how the merge query went. But I suspect we'll never see the error message!

(BTW: I think it's much better code style do say if (positive) {} else {}, rather than if (negative) {} else {}, as the latter form makes it potentially quite hard to figure out what the else bit means.)