Fix show_header bug that caused PHP error on load_user=false
Fix show_header bug that caused PHP error on load_user=false

Header was trying to get information from user object when
none existed if the load_user parameter was false. Made check on
whether load_user to stop this from happening.

charliemeyer/geni-portal,tcmitchell/geni-portal,charliemeyer/geni-portal,tcmitchell/geni-portal,charliemeyer/geni-portal,tcmitchell/geni-portal,tcmitchell/geni-portal,charliemeyer/geni-portal,charliemeyer/geni-portal,tcmitchell/geni-portal