Fix TypeError on Generation

After several page build fails, this seems to have fixed up the following error:

lib/jekyll/excerpt.rb:108:in `partition': type mismatch: NilClass given (TypeError)

site/_config.yml

@@ -2,4 +2,4 @@ pygments: true
 relative_permalinks: false
 gauges_id: 503c5af6613f5d0f19000027
 permalink: /news/:year/:month/:day/:title
-excerpt_separator: 
+excerpt_separator: noifniof3nioaniof3nioafafinoafnoif