Index: branches/RC/core/kernel/utility/debugger.php
===================================================================
diff -u -r8929 -r9639
--- branches/RC/core/kernel/utility/debugger.php	(.../debugger.php)	(revision 8929)
+++ branches/RC/core/kernel/utility/debugger.php	(.../debugger.php)	(revision 9639)
@@ -584,7 +584,8 @@
 			 */
 			function isGecko()
 			{
-				return strpos(strtolower($_SERVER['HTTP_USER_AGENT']), 'firefox') !== false;
+				// we need isset because we may run scripts from shell with no user_agent at all
+				return isset($_SERVER['HTTP_USER_AGENT']) && strpos(strtolower($_SERVER['HTTP_USER_AGENT']), 'firefox') !== false;
 			}
 
 			/**