Undefined Index & Variable

Problem/Motivation

The site was working without issue, on 10/7 the styling broke and the logs started producing the following Notices.
Notice: Undefined index: display_breadcrumb in zen_breadcrumb() (line 101 of /home4/public_html/v2/sites/all/themes/zen2/template.php).
Notice: Undefined variable: add_respond_js in include() (line 29 of /home4/public_html/v2/sites/all/themes/zen/templates/html.tpl.php).

Below are the two lines of code:

if ($add_html5_shim and !$add_respond_js):

if ($variables['display_breadcrumb'] && !empty($variables['breadcrumb']))

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes