backtrace: check the parameter before use it

git-svn-id: https://svn.fournier38.fr/svn/ProgSVN/trunk@3659 bf3deb0d-5f1a-0410-827f-c0cc1f45334c

backtrace.php

@@ -6,9 +6,12 @@ class backtrace
 {
   /** Display the backtrace in the browser
     * use: \backtrace::show (debug_backtrace ());
+    * @param array $backtrace The backtrace to display
     */
   public static function show ($backtrace)
   {
+    if (! is_array ($backtrace))
+      throw new \Exception ("Backtrace invalid: not an array", 500);
     echo "<pre>Debug BackTrace:\n";
     foreach ($backtrace as $key=>$back)
     {