Variable Declared in a Plugin Not Initialized in Error Pages

[lordfkiller]

Hello.

I have created a plugin for global_start hook with execution order of 5.

PHP Code:

ob_start();
$sth_currentloc_enc = urlencode('http://forums.domain.com'.$_SERVER['REQUEST_URI']);
ob_end_clean(); 


As you can see, it declares and initializes a variable called $sth_currentloc_enc which contains URL-encoded URL of current page.
The problem is that in error pages, the variable is not set(returns ""). Though it works well in other pages like home page etc.

Any help is kindly appreciated.