Modify pickKey to examine parent array before nested arrays.

include/functions.inc.php

@@ -1149,6 +1149,10 @@ function &serendipity_pickKey(&$array, $key, $default) {
         return $default;
     }
 
+    // array_key_exists() copies array, so is much slower.
+    if (in_array($key, array_keys($array))) {
+        return $array[$key];
+    }
     foreach($array AS $child) {
         if (is_array($child) && isset($child[$key]) && !empty($child[$key])) {
             return $child[$key];