Removes unnecessary test and ensures getResponseHeader returns null if the header does not exist.
Removes unnecessary test and ensures getResponseHeader returns null if the header does not exist.

quiaro/request-agent,demetr84/Jquery,jcutrell/jquery,kpozin/jquery-nodom,RubyLouvre/jquery,chitranshi/jquery,sancao2/jquery,sancao2/jquery,hoorayimhelping/jquery,diracdeltas/jquery,dtjm/jquery,jquery/jquery,fat/jquery,ilyakharlamov/jquery-xul,jcutrell/jquery,npmcomponent/component-jquery,eburgos/jquery,Karyotyper/jquery,demetr84/Jquery,Karyotyper/jquery,eburgos/jquery,npmcomponent/component-jquery,eburgos/jquery,diracdeltas/jquery,fat/jquery,jquery/jquery,diracdeltas/jquery,roytoo/jquery,roytoo/jquery,gnarf/jquery,RubyLouvre/jquery,sancao2/jquery,rwaldron/jquery,Karyotyper/jquery,roytoo/jquery,scottjehl/jquery,dtjm/jquery,jquery/jquery,ilyakharlamov/jquery-xul,chitranshi/jquery,praveen9102/Shazam,isaacs/jquery,praveen9102/Shazam,kpozin/jquery-nodom,hoorayimhelping/jquery,rwaldron/jquery,isaacs/jquery,gnarf/jquery,scottjehl/jquery