fixed compatibility with PHP 5.2 and simplify code a bit

diff --git a/lib/Twig/Error.php b/lib/Twig/Error.php
index a2ffd35..e32c5c9 100644 (file)
--- a/lib/Twig/Error.php
+++ b/lib/Twig/Error.php
@@ -172,7 +172,7 @@ class Twig_Error extends Exception
         $file = $r->getFileName();
 
         $exceptions = array($e = $this);
-        while ($e = $e->getPrevious()) {
+        while (method_exists($e, 'getPrevious') && $e = $e->getPrevious()) {
             $exceptions[] = $e;
         }