Updated author-profile.html in the event that there is no authors.yml…

… file.

_includes/author-profile.html

@@ -1,6 +1,6 @@
 {% include base_path %}
 
-{% if page.author %}
+{% if page.author and site.data.authors[page.author] %}
   {% assign author = site.data.authors[page.author] %}{% else %}{% assign author = site.author %}
 {% endif %}