Update Load.php

Attempt to prevent a bunch of Undefined Index errors for both 'seed' and 'browser_cache' (ip = ::1) generated in the error log using an obsolete web browser (i.e. Safari 4.1.3).  Isset can get undefined errors when an array key is not defined.  Using array_key_exists solves the undefined key problem.  The proposed changes assume that the keys can not be better defined elsewhere?