"Object reference not set to an instance of an object.&

I am developing a website using Sitefinity 4.1 and it worked great. However, since I changed one page's "Use this page only to group other pages" and "This page redirects to another page" options, I am getting "Object reference not set to an instance of an object." JavaScript error whenever I visit Design > Page Templates page. Please see attached screen shot.
When I tried to change the page's "Use this page only to group other pages" and "This page redirects to another page" options, I found that "Save Changes" button didn't work in some cases, but I don't know this was related to the JavaScript error I am getting.
Has anyone experienced this error? Any solution? I appreciate any help.

Hi Juyong,

The problems you are experiencing  are fixed in the internal build (ver. 4.1.1367) released this week.

 Also you can find  the solution in this post: http://www.sitefinity.com/devnet/forums/sitefinity-4-x/general-discussions/object-reference-not-set-to-an-instance-of-an-object-in-design-template.aspx

About your second issue there is a PITS logged. The ID is 5606.

As a workaround I can suggest you :

1.  Uncheck Use this page only to group other pages page
   
2.  Type any title in Title for search engines field
3.  Check again Use this page only to group other pages option and make any changes
4.  Click  Save Changes