diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index 2947245..89f5c48 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -627,13 +627,13 @@ function system_theme_settings_validate($form, &$form_state) {
 
   // If the user provided a path for a logo or favicon file, make sure a file
   // exists at that path.
-  if ($form_state['values']['logo_path']) {
+  if (!empty($form_state['values']['logo_path'])) {
     $path = _system_theme_settings_validate_path($form_state['values']['logo_path']);
     if (!$path) {
       form_set_error('logo_path', t('The custom logo path is invalid.'));
     }
   }
-  if ($form_state['values']['favicon_path']) {
+  if (!empty($form_state['values']['favicon_path'])) {
     $path = _system_theme_settings_validate_path($form_state['values']['favicon_path']);
     if (!$path) {
       form_set_error('favicon_path', t('The custom favicon path is invalid.'));
@@ -687,14 +687,14 @@ function system_theme_settings_submit($form, &$form_state) {
 
   // If the user uploaded a new logo or favicon, save it to a permanent location
   // and use it in place of the default theme-provided file.
-  if ($file = $values['logo_upload']) {
+  if (isset($values['logo_upload']) && $file = $values['logo_upload']) {
     unset($values['logo_upload']);
     $filename = file_unmanaged_copy($file->uri);
     $values['default_logo'] = 0;
     $values['logo_path'] = $filename;
     $values['toggle_logo'] = 1;
   }
-  if ($file = $values['favicon_upload']) {
+  if (isset($values['favicon_upload']) && $file = $values['favicon_upload']) {
     unset($values['favicon_upload']);
     $filename = file_unmanaged_copy($file->uri);
     $values['default_favicon'] = 0;