Add reject handlers to query() calls in OnDemandList

[neekfenwick]

This was raised as #241

[ghost]

This is actually just adding an error message as a child of the loading message div, which seems like it'd be awkward at best, and furthermore we've now fixed the code so that loading nodes are properly removed whether queries succeed or fail (see #351), so this code would now actually end up not showing anything.

See also my comment on #241 (comment)