fixed problem when missing base-url

lib/jekyll/scholar/tags/bibliography.rb

@@ -28,6 +28,9 @@ module Jekyll
         end
 
         content_tag :ol, references.join("\n")
+      rescue => e
+        debugger
+        warn e.message
       end
       
     end

lib/jekyll/scholar/utilities.rb

@@ -58,7 +58,7 @@ module Jekyll
       end
       
       def base_url
-        @base_url ||= site.config['baseurl'] || site.config['base_url'] || nil
+        @base_url ||= site.config['baseurl'] || site.config['base_url'] || ''
       end
       
       def details_path