Fixed a bug in the URL Helper where prep_url() could cause a PHP error on PHP versions < 5.1.2.
diff --git a/system/helpers/url_helper.php b/system/helpers/url_helper.php
index 7707d68..dad7611 100644
--- a/system/helpers/url_helper.php
+++ b/system/helpers/url_helper.php
@@ -446,7 +446,9 @@
 			return '';
 		}
 
-		if ( ! parse_url($str, PHP_URL_SCHEME))
+		$url = parse_url($str);
+		
+		if ( ! $url OR ! isset($url['scheme']))
 		{
 			$str = 'http://'.$str;
 		}