Bug 296305 fix error that occurs when using forward button dropdown with many entries

r=timeless sr=neil a=asa

xpfe/browser/resources/content/sessionHistoryUI.js

@@ -73,8 +73,8 @@ function FillHistoryMenu(aParent, aMenu)
             }
           break;
         case "forward":
-          end  = ((count-index) > MAX_HISTORY_MENU_ITEMS) ? index + MAX_HISTORY_MENU_ITEMS : count;
-          if ((index + 1) >= end) return false;
+          end  = ((count-index) > MAX_HISTORY_MENU_ITEMS) ? index + MAX_HISTORY_MENU_ITEMS : count - 1;
+          if ((index + 1) > end) return false;
           for (j = index + 1; j <= end; j++)
             {
               entry = sessionHistory.getEntryAtIndex(j, false);