I found out just recently that in some cases when you perform a blank search on a WordPress site you are redirected to the front page with an error message. If you encounter this issue simply apply the fix below, which modifies the blank search into a search for one space. This is enough to resolve the error page and land you on the search page.

Add the following code to your theme’s functions.php file to fix this annoying behavior:

if(!is_admin()){
	add_action('init', 'search_query_fix');
	function search_query_fix(){
		if(isset($_GET['s']) && $_GET['s']==''){
			$_GET['s']=' ';
		}
	}
}