Trying to fix errors

I have a whole bunch of errors in my error log that I am trying to fix. I have been successful in fixing some, but there are two so far that has me stumped.

The first error is:
Trying to get property of non-object in /home/hbco/wp-content/themes/londonlive-child/header.php on line 198

Here is what is on that line:
if($page_item->ID == $post->ID) { $selected = ‘ selected=”selected”‘; } else { $selected = ”; }

The second error is:

PHP Notice: get_the_author_email is deprecated since version 2.8.0! Use get_the_author_meta(’email’) instead. in /home/hbco/wp-includes/functions.php on line 3838

I can’t find where the get_the_author_email is?

Also, I am getting an error that is related to a plug-in, but the plug-in works. Do I try and fix it? The error is:

PHP Notice: Undefined index: debug in /home/hbco/wp-content/plugins/store-locator/sl-functions.php on line 1319, referer: https://www3.hunterdonbrewing.com/?cat=2

The page I need help with: [log in to see the link]