Catch error adding link to notebook list

Part of the fix for gh-223.

If a filename can't be decoded in the current encoding, Python escapes
the undecodable bytes as unpaired surrogates, which JS doesn't like
building a URL from.

This doesn't make the undecodable filename openable, but it stops it
from breaking the listing of other files.

The real fix is to set up the locale encoding correctly so that the
filenames can be decoded.

notebook/static/tree/js/notebooklist.js

@@ -295,7 +295,11 @@ define([
         for (var i=0; i<len; i++) {
             model = list.content[i];
             item = this.new_item(i+offset, true);
-            this.add_link(model, item);
+            try {
+                this.add_link(model, item);
+            } catch(err) {
+                console.log('Error adding link: ' + err)
+            }
         }
         // Trigger an event when we've finished drawing the notebook list.
         events.trigger('draw_notebook_list.NotebookList');