Sub-Module to use Twitter Avatars with Drupal Profiles

I am working on a solution for using Twitter avatars as the user profile picture in D7. I am not a developer but took a stab at converting the D6 module developed by @xenatt in issue #771882: Sub-module for showing Twitter avatars with Drupal profiles - include in the main Twitter package?

The module reported to be successful for D6 and I have taken it as far as my abilities will allow for D7. I am now getting an error message "Notice: Array to string conversion in rdf_preprocess_image() (line 772 of /.../modules/rdf/rdf.module)." when trying to access a user page.

I have attached the module and here is the code:

// $Id: twitter_avatar.module,v 1.1.2.6 2010/04/15 03:14:45 walkah Exp $

/**
 * 
 */
function twitter_avatar_preprocess_user_picture(&$variables) {
  $variables['picture'] = '';
  
  if (variable_get('user_pictures', 0)) {
	$pic_url = '';  
    $account = $variables['account'];
    $twitter_fdb = db_query("SELECT profile_image_url FROM {twitter_account} WHERE uid = :uid", array(':uid' => $account->uid))->fetchField();
	if (eregi("_normal.jpg$", $twitter_fdb)) { $pic_url = ereg_replace("_normal.jpg$","_bigger.jpg",$twitter_fdb); }
	elseif (eregi("_normal.JPG$", $twitter_fdb)) { $pic_url = ereg_replace("_normal.jpg$","_bigger.jpg",$twitter_fdb); }
	elseif (eregi("_normal.png$", $twitter_fdb)) { $pic_url = ereg_replace("_normal.png$","_bigger.png",$twitter_fdb); }
	elseif (eregi("_normal.PNG$", $twitter_fdb)) { $pic_url = ereg_replace("_normal.PNG$","_bigger.PNG",$twitter_fdb); }
	elseif (eregi("_normal.gif$", $twitter_fdb)) { $pic_url = ereg_replace("_normal.gif$","_bigger.gif",$twitter_fdb); }
	else { $pic_url = ereg_replace("_normal.GIF$","_bigger.GIF",$twitter_fdb); }
    if (!empty($account->name) && !empty($pic_url)) {
      $picture = $pic_url;
    }  elseif (!empty($account->picture) && file_exists($account->picture)) {
      $picture = file_create_url($account->picture);
    }
    elseif (variable_get('user_picture_default', '')) {
      $picture = variable_get('user_picture_default', '');
    } 

    if (isset($picture)) {
      $alt = t("@user's picture", array('@user' => $account->name ? $account->name : variable_get('anonymous', t('Anonymous'))));
      $variables['picture'] = theme('image', $picture, $alt, $alt, '', FALSE);
      if (!empty($account->uid) && user_access('access user profiles')) {
        $attributes = array('attributes' => array('title' => t('View user profile.')), 'html' => TRUE);
        $variables['picture'] = l($variables['picture'], "user/$account->uid", $attributes);
      }
    }
  }
}