Index: modules/system/system.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.module,v
retrieving revision 1.376
diff -u -F^f -r1.376 system.module
--- modules/system/system.module	5 Oct 2006 15:47:57 -0000	1.376
+++ modules/system/system.module	8 Oct 2006 00:57:37 -0000
@@ -352,7 +352,7 @@ function system_main_admin_page($arg = N
   usort($menu['children'], '_menu_sort');
   foreach ($menu['children'] as $mid) {
     $block = menu_get_item($mid);
-    if ($block['block callback'] && function_exists($block['block callback'])) {
+    if (isset($block['block callback']) && function_exists($block['block callback'])) {
       $arguments = isset($block['block arguments']) ? $block['block arguments'] : array();
       $block['content'] .= call_user_func_array($block['block callback'], $arguments);
     }
@@ -368,7 +368,7 @@ function system_main_admin_page($arg = N
  */
 function system_admin_menu_block($block) {
   $content = array();
-  if (is_array($block['children'])) {
+  if (isset($block['children']) && is_array($block['children'])) {
     usort($block['children'], '_menu_sort');
     foreach ($block['children'] as $mid) {
       $item = menu_get_item($mid);
@@ -1958,13 +1958,14 @@ function system_admin_compact_mode() {
  */
 function theme_admin_page($blocks) {
   $stripe = 0;
+  $container = array();
   foreach ($blocks as $block) {
     if ($block_output = theme('admin_block', $block)) {
       if (!$block['position']) {
         // perform automatic striping.
         $block['position'] = $stripe++ % 2 ? 'left' : 'right';
       }
-      $container[$block['position']] .= $block_output;
+      $container[$block['position']] = (isset($container[$block['position']]) ? $container[$block['position']] : '') . $block_output;
     }
   }
 
@@ -2043,7 +2044,7 @@ function theme_admin_block_content($cont
     $output = '<dl class="admin-list">';
     foreach ($content as $item) {
       $output .= '<dt>'. l($item['title'], $item['path']) .'</dt>';
-      $output .= '<dd>'. $item['description'] .'</dd>';
+      $output .= '<dd>'. (isset($item['description']) ? $item['description'] : '') .'</dd>';
     }
     $output .= '</dl>';
   }