Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.1052
diff -u -r1.1052 common.inc
--- includes/common.inc	26 Nov 2009 05:54:48 -0000	1.1052
+++ includes/common.inc	30 Nov 2009 17:13:00 -0000
@@ -3451,6 +3451,9 @@ drupal_load_stylesheet(
     // Change back directory.
     chdir($cwd);
   }
+  else {
+    return FALSE;
+  }
 
   return $contents;
 }
@@ -3498,6 +3501,9 @@ _drupal_load_stylesheet(
   $filename = $matches[1];
   // Load the imported stylesheet and replace @import commands in there as well.
   $file = drupal_load_stylesheet($filename);
+  if ($file === FALSE) {
+    return '@import url(' . $filename . ');';
+  }
   // Alter all url() paths, but not external.
   return preg_replace('/url\(([\'"]?)(?![a-z]+:)([^\'")]+)[\'"]?\)?;/i', 'url(\1' . dirname($filename) . '/', $file);
 }