Fixed null structure field in Library listing

_layouts/library.html

@@ -19,12 +19,15 @@ layout: default
           rules = data.reverse();
           libHTML = "";
           for (var i = 0; i < rules.length; i++) {
-              var title = rules[i]["communityname"]
+              var title = rules[i]["communityname"];
               if (title == null) { title = "Untitled"; }
               libHTML += "<h2 id='rulename'>" +
                   "<a href='/create/?r=" + rules[i]["ruleID"] + "'>" +
                   title + "</a></h2>\n";
-              libHTML += "<p>" + rules[i]["structure"] + "</p>\n\n";
+              var structure = rules[i]["structure"];
+              if (structure != null) {
+                  libHTML += "<p>" + structure + "</p>\n\n";
+              }
           }
           document.getElementById("libraryList").innerHTML = libHTML;
       });