? sites/default/modules
? sites/default/settings.php
Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.756.2.72
diff -u -p -r1.756.2.72 common.inc
--- includes/common.inc	6 Oct 2009 12:03:11 -0000	1.756.2.72
+++ includes/common.inc	28 Oct 2009 23:48:22 -0000
@@ -3207,7 +3207,10 @@ function drupal_get_schema($table = NULL
 
       // Invoke hook_schema for all modules.
       foreach (module_implements('schema') as $module) {
-        $current = module_invoke($module, 'schema');
+        // Cast the result of hook_schema() to an array, as a NULL return value
+        // would cause array_merge() to set the $schema variable to NULL as well.
+        // That would break modules which use $schema further down the line.
+        $current = (array) module_invoke($module, 'schema');
         _drupal_initialize_schema($module, $current);
         $schema = array_merge($schema, $current);
       }