- Patch #921098 by munzirtaha: !is_null() should be replaced by isset() because it's faster.

includes/file.inc

@@ -1296,7 +1296,7 @@ function file_space_used($uid = NULL, $status = FILE_STATUS_PERMANENT) {
   $query = db_select('file_managed', 'f');
   $query->condition('f.status', $status);
   $query->addExpression('SUM(f.filesize)', 'filesize');
-  if (!is_null($uid)) {
+  if (isset($uid)) {
     $query->condition('f.uid', $uid);
   }
   return $query->execute()->fetchField();

modules/field/field.crud.inc

@@ -762,7 +762,7 @@ function _field_write_instance($instance, $update = FALSE) {
   // If no weight specified, make sure the field sinks at the bottom.
   if (!isset($instance['widget']['weight'])) {
     $max_weight = field_info_max_weight($instance['entity_type'], $instance['bundle'], 'form');
-    $instance['widget']['weight'] = !is_null($max_weight) ? $max_weight + 1 : 0;
+    $instance['widget']['weight'] = isset($max_weight) ? $max_weight + 1 : 0;
   }
   // Check widget module.
   $widget_type = field_info_widget_types($instance['widget']['type']);
@@ -788,7 +788,7 @@ function _field_write_instance($instance, $update = FALSE) {
     // If no weight specified, make sure the field sinks at the bottom.
     if (!isset($display['weight'])) {
       $max_weight = field_info_max_weight($instance['entity_type'], $instance['bundle'], $view_mode);
-      $display['weight'] = !is_null($max_weight) ? $max_weight + 1 : 0;
+      $display['weight'] = isset($max_weight) ? $max_weight + 1 : 0;
     }
     $instance['display'][$view_mode] = $display;
   }

modules/system/system.admin.inc

@@ -639,7 +639,7 @@ function system_theme_settings($form, &$form_state, $key = '') {
     }
 
     // Restore the original current theme.
-    if (!is_null($default_theme)) {
+    if (isset($default_theme)) {
       $GLOBALS['theme_key'] = $default_theme;
     }
     else {