Replace 'null' description by something more sensible.

pd/nw/dialog_search.html

@@ -134,7 +134,7 @@ function display_toc() {
         a.title = doc.id;
         header = document.createElement("h3");
         header.appendChild(a);
-        text_node = document.createTextNode(doc.description);
+        text_node = document.createTextNode(doc.description?doc.description:"no description");
         div.appendChild(header);
         div.appendChild(text_node);
         results_elem.appendChild(div);
@@ -439,7 +439,7 @@ function display_doc(doc) {
     a.title = doc.id;
     header = document.createElement("h3");
     header.appendChild(a);
-    text_node = document.createTextNode(doc.description);
+    text_node = document.createTextNode(doc.description?doc.description:"no description");
     div.appendChild(header);
     div.appendChild(text_node);
     results_elem.appendChild(div);