Blogger Dashboard Layour Menu Error

Blogger Layout on Dashboard Blogger make your blog design easily, drag and drop to move widget accordance with our wishes, to add some gadget just click on Add a Gadget widget and choose what gadget you want use. 

But how if that Layout menu getting error ?

Yesterday, I get my Layout blank, nothing invisible to click, all gadget gone only empty screen display, but my blog page display is fine, I am searching from search engine about this issue but found nothing, the display as shown in the following image:

I'm really confused and do not know what to do, but suddenly when clicking to preview menu on Edit HTML Template, I see the error message as below:

LHS of numeric is null 8 , bla bla bla bla

So imediatelly go to line 8 on Edit HTML template and found wrong meta descriptions writing, that is dynamic meta content which use expr:content  but written using static content, example:

<meta expr:content='YOUR-DESCRIPTION' name='description'/>
 
Should be: 

<meta expr:content='data:blog.pageTitle' name='description'/>

After doing repairs on the above meta content, Layout menu on Blogger Dashboard back to normal and my problem is solved. I am very happy to solved it by my self, hehehehe...

I hope this can be useful for some who get same error with me, thanks.