fix bug 428: blank page when gd extension missing

svn merge -r1377:1378 from branch 1.6 into trunk


git-svn-id: http://piwigo.org/svn/trunk@1379 68402e56-0260-453c-a942-63ccdbb3a9ee

admin/thumbnail.php

@@ -40,6 +40,11 @@ function RatioResizeImg($path, $newWidth, $newHeight, $tn_ext)
 {
   global $conf, $lang, $page;
 
+  if (!function_exists('gd_info'))
+  {
+    return;
+  }
+
   $filename = basename($path);
   $dirname = dirname($path);