Upgrade problem Undefined variable: header.tpl

HI there, I am new to open cart and was trying to upgrade from v1.5.2.1 to 1.5.5.1
and got a lot of errors on the main page here is the website http://bonsaistore.ca/TROPEX/
Tried to find how to fix it but still can't, please let me know if you have any suggestions.


Notice: Undefined variable: filter_name in /home1/bonsaist/public_html/TROPEX/catalog/view/theme/theme036/template/common/header.tpl on line 142
Notice: Undefined index: category_id in /home1/bonsaist/public_html/TROPEX/catalog/view/theme/theme036/template/common/header.tpl on line 162Notice: Undefined variable: category_id in /home1/bonsaist/public_html/TROPEX/catalog/view/theme/theme036/template/common/header.tpl on line 162

You will need to get the latest version of your theme as it's out of date. Upgrading doesn't upgrade themes