incredible thing in Smarty 3-Collection of common programming errors

I wrote small plugin for smarty 3 to allocate my files in case of theme options. It work fine all the time, but i choose new template for new project. And discover something mad!

{block name="css_load"}
        
         
{/block}

Normal code isn’t it? But it throw exception:

Syntax error in template "\www\themes\default\base.tpl"  on line 12 ""  - Unexpected "'plugins/bootstrap/css/bootstrap.min.css'", expected one of: "identifier"    

And how to fix it? Just add an extra “s” in path string like this:

{block name="css_load"}
        
         
{/block}

And it will work fine without exception!

WHAT IS THAT?!

Smarty version 3.1.15

Template: metronic 1.4