Call to a member function get_url_queryvalues() on a non-object

Getting this one on an Acquia hosted Drupal 6 site running on 8 servers. NewRelic came up with the root cause here:

in apachesolr_l called at /mnt/www/html//docroot/sites/all/modules/contrib/apachesolr/apachesolr.module (1816)

The problem:

/**
 * Static getter/setter for the current query
 *
 * @todo reverse the order of parameters in future branches.
 */
function apachesolr_current_query($query = NULL, $namespace = 'apachesolr_search') {
  static $saved_query = array();

  if (is_object($query)) {
    $saved_query[$namespace] = clone $query;
  }

  return is_object($saved_query[$namespace]) ? clone $saved_query[$namespace] : NULL;
}

/*** As you can see, the function above can return NULL in some cases! ***/

[...]

  // Retain GET parameters that ApacheSolr knows nothing about.
  $query = apachesolr_current_query();
  $get = array_diff_key($_GET, array('q' => 1, 'page' => 1), $options['query'], $query->get_url_queryvalues());
  $options['query'] += $get;

/*** The code above does absolutely no check on $query being NULL or not, resulting in the error mentioned in the subject of this issue. ***/

Proposed solution:

  // Retain GET parameters that ApacheSolr knows nothing about.
  $query = apachesolr_current_query();
  if ($query) {
    $get = array_diff_key($_GET, array('q' => 1, 'page' => 1), $options['query'], $query->get_url_queryvalues());
    $options['query'] += $get;
  }

Whatever the cause of the apachesolr_current_query() returning NULL doesn't even matter in this example, the state should be checked before simply assuming it's an object and handling it as such.