Errors on post-template.php lines 721 & 516

I receive these 2 errors and do not know how to fix them. I need some help please. I am running: WordPress 4.2.2 running BLDR theme.

Warning: array_unique() [function.array-unique]: The argument should be an array in /home/content/n/o/s/myusername/html/wp-includes/post-template.php on line 721

Warning: join() [function.join]: Invalid arguments passed in /home/content/n/o/s/myusername/html/wp-includes/post-template.php on line 516
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This is where I first saw the error: https://homeschoolingonashoestring.com/list-of-search-engines/www.crosssearch.com
I realized the link itself is an error, but it brought up the 2 errors above. I tried it again using another page name that I know I do not have and it brings up the same error. So while it says the error is in post-template.php, I think the post is coming up for any 404 error. I cannot find post-template.php in the editor.
I would appreciate some help with this please.
I really like this theme and would love it to work as the designer/author intended.
Thanks in advance!
Jodi