Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.1212
diff -u -p -r1.1212 common.inc
--- includes/common.inc	1 Sep 2010 20:08:17 -0000	1.1212
+++ includes/common.inc	3 Sep 2010 11:14:46 -0000
@@ -2829,6 +2829,11 @@ function drupal_get_css($css = NULL) {
   $previous_item = array();
   foreach ($css as $key => $item) {
     if ($item['type'] == 'file') {
+      // Check if CSS file exists.
+      if (!file_exists($key)) {
+        unset($css[$key]);
+        continue;
+      }
       // If defined, force a unique basename for this file.
       $basename = isset($item['basename']) ? $item['basename'] : basename($item['data']);
       if (isset($previous_item[$basename])) {